assignment statement c

Assignment Statement in C

How to assign values to the variables? C provides an assignment operator for this purpose, assigning the value to a variable using assignment operator is known as an assignment statement in C.

The function of this operator is to assign the values or values in variables on right hand side of an expression to variables on the left hand side.

The syntax of the assignment expression

Variable = constant / variable/ expression;

The data type of the variable on left hand side should match the data type of constant/variable/expression on right hand side with a few exceptions where automatic type conversions are possible.

Examples of assignment statements,

b = c ; /* b is assigned the value of c */ a = 9 ; /* a is assigned the value 9*/ b = c+5; /* b is assigned the value of expr c+5 */

The expression on the right hand side of the assignment statement can be:

An arithmetic expression; A relational expression; A logical expression; A mixed expression.

The above mentioned expressions are different in terms of the type of operators connecting the variables and constants on the right hand side of the variable. Arithmetic operators, relational

Arithmetic operators, relational operators and logical operators are discussed in the following sections.

For example, int a; float b,c ,avg, t; avg = (b+c) / 2; /*arithmetic expression */ a = b && c; /*logical expression*/ a = (b+c) && (b<c); /* mixed expression*/

Assignment Statement Forms

This is one of the most common forms of Assignment Statements. Here the Variable name is defined, initialized, and assigned a value in the same statement. This form is generally used when we want to use the Variable quite a few times and we do not want to change its value very frequently.

Tuple Assignment

Generally, we use this form when we want to define and assign values for more than 1 variable at the same time. This saves time and is an easy method. Note that here every individual variable has a different value assigned to it.

(Code In Python)

Sequence Assignment

(Code in Python)

Multiple-target Assignment or Chain Assignment

In this format, a single value is assigned to two or more variables.

Augmented Assignment

In this format, we use the combination of mathematical expressions and values for the Variable. Other augmented Assignment forms are: &=, -=, **=, etc.

Browse more Topics Under Data Types, Variables and Constants

Concept of Data types
Built-in Data Types
Constants in Programing Language
Access Modifier
Variables of Built-in-Datatypes
Declaration/Initialization of Variables
Type Modifier

Few Rules for Assignment Statement

Few Rules to be followed while writing the Assignment Statements are:

Variable names must begin with a letter, underscore, non-number character. Each language has its own conventions.
The Data type defined and the variable value must match.
A variable name once defined can only be used once in the program. You cannot define it again to store other types of value.
If you assign a new value to an existing variable, it will overwrite the previous value and assign the new value.

FAQs on Assignment Statement

Q1. Which of the following shows the syntax of an assignment statement ?

variablename = expression ;
expression = variable ;
datatype = variablename ;
expression = datatype variable ;

Answer – Option A.

Q2. What is an expression ?

Same as statement
List of statements that make up a program
Combination of literals, operators, variables, math formulas used to calculate a value
Numbers expressed in digits

Answer – Option C.

Q3. What are the two steps that take place when an assignment statement is executed?

Evaluate the expression, store the value in the variable
Reserve memory, fill it with value
Evaluate variable, store the result
Store the value in the variable, evaluate the expression.

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7 Assignment Expressions

As a general concept in programming, an assignment is a construct that stores a new value into a place where values can be stored—for instance, in a variable. Such places are called lvalues (see Lvalues ) because they are locations that hold a value.

An assignment in C is an expression because it has a value; we call it an assignment expression . A simple assignment looks like

We say it assigns the value of the expression value-to-store to the location lvalue , or that it stores value-to-store there. You can think of the “l” in “lvalue” as standing for “left,” since that’s what you put on the left side of the assignment operator.

However, that’s not the only way to use an lvalue, and not all lvalues can be assigned to. To use the lvalue in the left side of an assignment, it has to be modifiable . In C, that means it was not declared with the type qualifier const (see const ).

The value of the assignment expression is that of lvalue after the new value is stored in it. This means you can use an assignment inside other expressions. Assignment operators are right-associative so that

is equivalent to

This is the only useful way for them to associate; the other way,

would be invalid since an assignment expression such as x = y is not valid as an lvalue.

Warning: Write parentheses around an assignment if you nest it inside another expression, unless that is a conditional expression, or comma-separated series, or another assignment.

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Assignment Operators in C

In C, the assignment operator stores a certain value in an already declared variable. A variable in C can be assigned the value in the form of a literal, another variable or an expression. The value to be assigned forms the right hand operand, whereas the variable to be assigned should be the operand to the left of = symbol, which is defined as a simple assignment operator in C. In addition, C has several augmented assignment operators.

The following table lists the assignment operators supported by the C language −

Simple assignment operator (=)

The = operator is the most frequently used operator in C. As per ANSI C standard, all the variables must be declared in the beginning. Variable declaration after the first processing statement is not allowed. You can declare a variable to be assigned a value later in the code, or you can initialize it at the time of declaration.

You can use a literal, another variable or an expression in the assignment statement.

Once a variable of a certain type is declared, it cannot be assigned a value of any other type. In such a case the C compiler reports a type mismatch error.

In C, the expressions that refer to a memory location are called "lvalue" expressions. A lvalue may appear as either the left-hand or right-hand side of an assignment.

On the other hand, the term rvalue refers to a data value that is stored at some address in memory. A rvalue is an expression that cannot have a value assigned to it which means an rvalue may appear on the right-hand side but not on the left-hand side of an assignment.

Variables are lvalues and so they may appear on the left-hand side of an assignment. Numeric literals are rvalues and so they may not be assigned and cannot appear on the left-hand side. Take a look at the following valid and invalid statements −

Augmented assignment operators

In addition to the = operator, C allows you to combine arithmetic and bitwise operators with the = symbol to form augmented or compound assignment operator. The augmented operators offer a convenient shortcut for combining arithmetic or bitwise operation with assignment.

For example, the expression a+=b has the same effect of performing a+b first and then assigning the result back to the variable a.

Similarly, the expression a<<=b has the same effect of performing a<<b first and then assigning the result back to the variable a.

Here is a C program that demonstrates the use of assignment operators in C:

When you compile and execute the above program, it produces the following result −

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C Assignment Operators

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An assignment operation assigns the value of the right-hand operand to the storage location named by the left-hand operand. Therefore, the left-hand operand of an assignment operation must be a modifiable l-value. After the assignment, an assignment expression has the value of the left operand but isn't an l-value.

assignment-expression : conditional-expression unary-expression assignment-operator assignment-expression

assignment-operator : one of = *= /= %= += -= <<= >>= &= ^= |=

The assignment operators in C can both transform and assign values in a single operation. C provides the following assignment operators:

In assignment, the type of the right-hand value is converted to the type of the left-hand value, and the value is stored in the left operand after the assignment has taken place. The left operand must not be an array, a function, or a constant. The specific conversion path, which depends on the two types, is outlined in detail in Type Conversions .

Assignment Operators

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cppreference.com

Assignment operators.

Assignment and compound assignment operators are binary operators that modify the variable to their left using the value to their right.

[ edit ] Simple assignment

The simple assignment operator expressions have the form

Assignment performs implicit conversion from the value of rhs to the type of lhs and then replaces the value in the object designated by lhs with the converted value of rhs .

Assignment also returns the same value as what was stored in lhs (so that expressions such as a = b = c are possible). The value category of the assignment operator is non-lvalue (so that expressions such as ( a = b ) = c are invalid).

rhs and lhs must satisfy one of the following:

both lhs and rhs have compatible struct or union type, or..
rhs must be implicitly convertible to lhs , which implies
both lhs and rhs have arithmetic types , in which case lhs may be volatile -qualified or atomic (since C11)
both lhs and rhs have pointer to compatible (ignoring qualifiers) types, or one of the pointers is a pointer to void, and the conversion would not add qualifiers to the pointed-to type. lhs may be volatile or restrict (since C99) -qualified or atomic (since C11) .
lhs is a (possibly qualified or atomic (since C11) ) pointer and rhs is a null pointer constant such as NULL or a nullptr_t value (since C23)

[ edit ] Notes

If rhs and lhs overlap in memory (e.g. they are members of the same union), the behavior is undefined unless the overlap is exact and the types are compatible .

Although arrays are not assignable, an array wrapped in a struct is assignable to another object of the same (or compatible) struct type.

The side effect of updating lhs is sequenced after the value computations, but not the side effects of lhs and rhs themselves and the evaluations of the operands are, as usual, unsequenced relative to each other (so the expressions such as i = ++ i ; are undefined)

Assignment strips extra range and precision from floating-point expressions (see FLT_EVAL_METHOD ).

In C++, assignment operators are lvalue expressions, not so in C.

[ edit ] Compound assignment

The compound assignment operator expressions have the form

The expression lhs @= rhs is exactly the same as lhs = lhs @ ( rhs ) , except that lhs is evaluated only once.

[ edit ] References

C17 standard (ISO/IEC 9899:2018):
6.5.16 Assignment operators (p: 72-73)
C11 standard (ISO/IEC 9899:2011):
6.5.16 Assignment operators (p: 101-104)
C99 standard (ISO/IEC 9899:1999):
6.5.16 Assignment operators (p: 91-93)
C89/C90 standard (ISO/IEC 9899:1990):
3.3.16 Assignment operators

[ edit ] See Also

Operator precedence

[ edit ] See also

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Assignment Statement (=) in C Language

Assignment Statement in C language is a statement that assigns or set a value to a variable during program execution. Assignement statements in programming allows the programmer to change or set the value stored in variable using Assignment(=) Operator. The process of assigning the value to a variable using the assignment(=) operator is known as an assignment statement in C. Assignment(=) Operator Assigns The value or value in a variable on right hand side to the variable on the left hand side. The data type of the variable on right hand side should match to the data type of variable or constant or expression on right hand side. C Language has different (types) ways to assigns values to variable, we will learn from the diagram given below.

Syntax :1.Basic Assignment statement

Data Type Variable_name = variable/ constant /expression; The Variable_name is assigned the values in variable or constants or expression. The data type of the variable/ constant/expression on right hand side should match to the left hand side variable Variable_name with a few exceptions where automatic type conversions are possible.

Naming Rules or conventions for Assignment Statement

Programmer need to follow some Rules while writing the Assignment Statements in C program: 1. Variable names should not begin or start with number. Variable name can a letter, underscore, non-number any character like alphabet,underscore. 2. A new value assigned to an existing variable will overwrite the previous value and assign the new value to the variable. 3. The Data type defined and the variable value must match. 4.All the statements declaration must end with a semi-colon. (;) 5. The name of variable must be meaningful and clearly describe the purpose of variable name. 6.Duplicate name of variable is not allowed i.e the name once defined can only be used once in the program. programmer cannot redefine it to store other types of value.

Example 1: C program to illustrates the use of Simple Assignment statement .

/* e.g. C program to illustrate the use of simple Assignment statement or basic of assignment statements */ #include<stdio.h> int main() { int a,b,c; float avg; a = 9 ; c = 10 ; b = c ; printf("\n a=%d",a); printf("\n b=%d",b); printf("\n c=%d",c); b = c+3; printf("\n Value of b after b=c+3-->%d",b); avg = (b+c) / 2.0; printf("\n Value of avg=%.2f",avg); a = b && c; printf("\n a=b&&c--->%d",a); a = (b+c) && (b <c); printf("\n a=(b+c) && (b <c)--->%d",a); return(0); } Output: a=9 b=10 c=10 Value of b after b=c+3-->13 Value of avg=11.50 a=b&&c--->1 a=(b+c) && (b <c)--->0

Program Explanation: 1. In the above program a,b,c is declared as integer variable to store the numbers where as avg is declared as float. int a,b,c; float avg; 2. a = 9 ; c = 10 ; b = c ; variable a is assigned value 9. variable c is assigned value 10. and b is assigned the value of c. Here value of b is 10 .i.e. b=10 3. printf("\n a=%d",a); printf("\n b=%d",b); printf("\n c=%d",c); The above statements displays the integer values of variable a,b,c a=9 b=10 c=10 4. b = c+3; printf("\n Value of b after b=c+3-->%d",b); here 3 is added in c(value of vaiable c is 10) it becomes 13 and value 13 is assigned to left hand side variable b , here b is 13 i.e. b=13. the printf() displays output " Value of b after b=c+3--->13". 5. avg = (b+c) / 2.0; printf("\n Value of avg=%.2f",avg); After execution of a=(b+c)/2.0 the value of a is 11.50 so the output shown by printf() is "Value of avg=11.50". 6. a = b && c; printf("\n a=b&&c--->%d",a); Logical anding operation is performed on the values in the variables a and b. The value of c=10 and the value of b=13. After succesful execution of this statement value of variable a is 1 or 'true'. Any value in a variable except 'zero' (0 i.e false) is considered 'true' or 1. The variable a is assigned to the integer value 1 which is true. so a=1 && 1 is a=1 or a=true && true is a=true or a=1. printf("\n a=b&&c--->%d",a); displays output a=b&&c---->1 7. a = (b+c) && (b <c); printf("\n a=(b+c) && (b <c)--->%d",a); here expression (b+c) is true(1) and (b <c) is false(0). so the entire expression evaluates to false(0) and the value is assigned to the variable a i.e a=0. the printf() display the message " a=(b+c) && (b <c)--->0 "

2.Compound Assignment: As we learn in above section the simple assignment statement is used to assign values in right hand side variable to left hand side variable using = operator. A compound assignment operator has a shorter syntax to assign the result. A compound assignment operator or statements are used to do mathematical operation in shortcut. Two operands needs to perform the compound assignment operations. The operation is performed on the two operands before the result is assigned to the first operand. compound assignment operator are binary operators that modify the variable to their left hand side using the value or variable to their right.

Syntax: expression1+= expression2; These type of expression can also be written in expanded form, that is expression1=expression1+expression2;

+= Operator is called compound assignment operator. C Language provides the following list of compound Assignment Operators. 1. += plus equal to += is Addition and Assignment operators. It add the value of the variable1 and variable2 and assigns the result to variable1. e.g. X+=Y In the above expression the addition of values in X and Y is performd and assigns result to X. The expression X+=Y is same as X=X+Y 2. -= minus equal to -= is Subtraction and Assignment operators. It Subtract the value of the variable2 from variable1 and assigns the result to variable1. e.g. X-=Y In the above expression the subtraction is performd,the value of X is subtracted from the value in X and assigns result to X. The expression X-=Y is same as X=X-Y 3. *= Multiplication equal to *= is Multiplication and Assignment operators. It Multiply the value of the variable1 and variable2 and assigns the result to variable1. e.g. X*=Y In the above expression the Multiplication is performd,the value of X is Multiplyed to the value in Y and assigns result to X. The expression X*=Y is same as X=X*Y 4. /= Division equal to *= is Division and Assignment operators. It Divides the value of the variable1 byvariable2 and assigns the result to variable1. e.g. X/=Y In the above expression the Division is performd,the value of X is Divided by the value in Y and assigns result to X. The expression X/=Y is same as X=X/Y 5. %= Modulus equal to %= is Modulus and Assignment operators. It Divides the value of the variable1 byvariable2 and assigns the remainder to variable1. e.g. X%=Y In the above expression the Division is performd,the value of X is Divided by the value in Y and assigns remainder to X. The expression X%=Y is same as X=X%Y 6. &= Bitwise and equal to &= is Bitwise AND and Assignment operators. It performs the bitwise AND with variable1 and variable2 and assigns the result to variable1. e.g. X&=Y In the above expression the bitwise anding operation is performd, after executing the X&=Y expression the result is assigned to X. The expression X&=Y is same as X=X&Y 7. |= Bitwise OR equal to != is Bitwise OR Assignment operators. It performs the bitwise OR with variable1 and variable2 and assigns the result to variable1. e.g. X|=Y In the above expression the bitwise OR operation is performd, after executing the X|=Y expression the result is assigned to X. The expression X|=Y is same as X=X|Y 8. ^= Bitwise XOR equal to ^= is Bitwise XOR Assignment operators. It performs the bitwise XOR with variable1 and variable2 and assigns the result to variable1. e.g. X^=Y In the above expression the bitwise XOR operation is performd, after executing the X^=Y expression the result is assigned to X. The expression X^=Y is same as X=X^Y. 9. Bitwise left shift and equal to e.g. X In the above expression the bitwise left shift operation is performd, after executing the X The expression X 10. >>= Bitwise right shift and equal to >>= is Bitwise Right Shift and Assignment operators. It performs the bitwise Right shift with variable1 and assigns the result to variable1. e.g. X>>=Y In the above expression the bitwise right shift operation is performd, after executing the X>>=Y expression the result is assigned to X. The expression X>>=Y is same as X=X>>Y Lets Learn and practice The Assigment operator in detail using the following C program.

2. Assignment Operator complete C Program.

#include <stdio.h> int main() { /* Simple Assignment*/ int x,i; int y,j; float c=30.0; float d=5.0; /*Nested or Multiple Assignment */ x = i = 5; y = j = 3; /*Compound Assignment*/ x += y; printf("After Add and Assign :%d \n",x); i -= j; printf("After Subtract and Assign :%d \n",i); x *= y; printf("After Multiple and Assign :%d \n",x); c /= d; printf("After Divide and Assign :%f \n",c); j %= i; printf("After Modulo and Assign :%d \n",j); j &= i; printf("After Bitwise And and Assign :%d \n",j); j |= i; printf("After Bitwise OR and Assign :%d \n",j); x ^= y; printf("After Bitwise XOR and Assign :%d \n",a); x printf ("After Bitwise Left Shift and Assign :%d \n",a); x >>= 3; printf ("After Bitwise Right Shift and Assign :%d \n",a); return(0); }

Output: After Add and Assign :8 After Subtract and Assign :2 After Multiple and Assign :24 After Divide and Assign :6.000000 After Modulo and Assign :1 After Bitwise And and Assign :0 After Bitwise OR and Assign :2 After Bitwise XOR and Assign :27 After Bitwise Left Shift and Assign :108 After Bitwise Right Shift and Assign :13

/** * C program to check leap year using conditional operator ? */ #include <stdio.h> int main() { int year; /* * Input the year from user */ printf("Enter any year: "); scanf("%d", &year); /* * If year%4==0 and year%100==0 then * print leap year * else if year%400==0 then * print leap year * else * print common year */ (year%4==0 && year%100!=0) ? printf("LEAP YEAR") : (year%400 ==0 ) ? printf("LEAP YEAR") : printf("COMMON YEAR"); return 0; } Output: Enter any year 2004 LEAP YEAR

/** * C program to check leap year using conditional operator ? */ #include <stdio.h> int main() { int year; /* * Input the year from user */ printf("Enter any year: "); scanf("%d", &year); /* If year%4==0 and year%100==0 then print leap year else if year%400==0 then print leap year else print common year */ (year%4==0 && year%100!=0) ? printf("LEAP YEAR") : (year%400 ==0 ) ? printf("LEAP YEAR") : printf("COMMON YEAR"); return 0; } Output: Enter any year 2004 LEAP YEAR

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Assignment and shorthand assignment operator in C

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Shorthand assignment

Assignment operator is used to assign value to a variable (memory location). There is a single assignment operator = in C. It evaluates expression on right side of = symbol and assigns evaluated value to left side the variable.

For example consider the below assignment table.

The RHS of assignment operator must be a constant, expression or variable. Whereas LHS must be a variable (valid memory location).

Shorthand assignment operator

C supports a short variant of assignment operator called compound assignment or shorthand assignment. Shorthand assignment operator combines one of the arithmetic or bitwise operators with assignment operator.

For example, consider following C statements.

The above expression a = a + 2 is equivalent to a += 2 .

Similarly, there are many shorthand assignment operators. Below is a list of shorthand assignment operators in C.

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Assignment operator in c.

Last Updated on June 23, 2023 by Prepbytes

This type of operator is employed for transforming and assigning values to variables within an operation. In an assignment operation, the right side represents a value, while the left side corresponds to a variable. It is essential that the value on the right side has the same data type as the variable on the left side. If this requirement is not fulfilled, the compiler will issue an error.

What is Assignment Operator in C language?

In C, the assignment operator serves the purpose of assigning a value to a variable. It is denoted by the equals sign (=) and plays a vital role in storing data within variables for further utilization in code. When using the assignment operator, the value present on the right-hand side is assigned to the variable on the left-hand side. This fundamental operation allows developers to store and manipulate data effectively throughout their programs.

Example of Assignment Operator in C

For example, consider the following line of code:

Types of Assignment Operators in C

Here is a list of the assignment operators that you can find in the C language:

Simple assignment operator (=): This is the basic assignment operator, which assigns the value on the right-hand side to the variable on the left-hand side.

Addition assignment operator (+=): This operator adds the value on the right-hand side to the variable on the left-hand side and assigns the result back to the variable.

x += 3; // Equivalent to x = x + 3; (adds 3 to the current value of "x" and assigns the result back to "x")

Subtraction assignment operator (-=): This operator subtracts the value on the right-hand side from the variable on the left-hand side and assigns the result back to the variable.

x -= 4; // Equivalent to x = x – 4; (subtracts 4 from the current value of "x" and assigns the result back to "x")

* Multiplication assignment operator ( =):** This operator multiplies the value on the right-hand side with the variable on the left-hand side and assigns the result back to the variable.

x = 2; // Equivalent to x = x 2; (multiplies the current value of "x" by 2 and assigns the result back to "x")

Division assignment operator (/=): This operator divides the variable on the left-hand side by the value on the right-hand side and assigns the result back to the variable.

x /= 2; // Equivalent to x = x / 2; (divides the current value of "x" by 2 and assigns the result back to "x")

Bitwise AND assignment (&=): The bitwise AND assignment operator "&=" performs a bitwise AND operation between the value on the left-hand side and the value on the right-hand side. It then assigns the result back to the left-hand side variable.

x &= 3; // Binary: 0011 // After bitwise AND assignment: x = 1 (Binary: 0001)

Bitwise OR assignment (|=): The bitwise OR assignment operator "|=" performs a bitwise OR operation between the value on the left-hand side and the value on the right-hand side. It then assigns the result back to the left-hand side variable.

x |= 3; // Binary: 0011 // After bitwise OR assignment: x = 7 (Binary: 0111)

Bitwise XOR assignment (^=): The bitwise XOR assignment operator "^=" performs a bitwise XOR operation between the value on the left-hand side and the value on the right-hand side. It then assigns the result back to the left-hand side variable.

x ^= 3; // Binary: 0011 // After bitwise XOR assignment: x = 6 (Binary: 0110)

Left shift assignment (<<=): The left shift assignment operator "<<=" shifts the bits of the value on the left-hand side to the left by the number of positions specified by the value on the right-hand side. It then assigns the result back to the left-hand side variable.

x <<= 2; // Binary: 010100 (Shifted left by 2 positions) // After left shift assignment: x = 20 (Binary: 10100)

Right shift assignment (>>=): The right shift assignment operator ">>=" shifts the bits of the value on the left-hand side to the right by the number of positions specified by the value on the right-hand side. It then assigns the result back to the left-hand side variable.

x >>= 2; // Binary: 101 (Shifted right by 2 positions) // After right shift assignment: x = 5 (Binary: 101)

Conclusion The assignment operator in C, denoted by the equals sign (=), is used to assign a value to a variable. It is a fundamental operation that allows programmers to store data in variables for further use in their code. In addition to the simple assignment operator, C provides compound assignment operators that combine arithmetic or bitwise operations with assignment, allowing for concise and efficient code.

FAQs related to Assignment Operator in C

Q1. Can I assign a value of one data type to a variable of another data type? In most cases, assigning a value of one data type to a variable of another data type will result in a warning or error from the compiler. It is generally recommended to assign values of compatible data types to variables.

Q2. What is the difference between the assignment operator (=) and the comparison operator (==)? The assignment operator (=) is used to assign a value to a variable, while the comparison operator (==) is used to check if two values are equal. It is important not to confuse these two operators.

Q3. Can I use multiple assignment operators in a single statement? No, it is not possible to use multiple assignment operators in a single statement. Each assignment operator should be used separately for assigning values to different variables.

Q4. Are there any limitations on the right-hand side value of the assignment operator? The right-hand side value of the assignment operator should be compatible with the data type of the left-hand side variable. If the data types are not compatible, it may lead to unexpected behavior or compiler errors.

Q5. Can I assign the result of an expression to a variable using the assignment operator? Yes, it is possible to assign the result of an expression to a variable using the assignment operator. For example, x = y + z; assigns the sum of y and z to the variable x.

Q6. What happens if I assign a value to an uninitialized variable? Assigning a value to an uninitialized variable will initialize it with the assigned value. However, it is considered good practice to explicitly initialize variables before using them to avoid potential bugs or unintended behavior.

Assignment Operators In C++

In C++, the assignment operator forms the backbone of many algorithms and computational processes by performing a simple operation like assigning a value to a variable. It is denoted by equal sign ( = ) and provides one of the most basic operations in any programming language that is used to assign some value to the variables in C++ or in other words, it is used to store some kind of information.

The right-hand side value will be assigned to the variable on the left-hand side. The variable and the value should be of the same data type.

The value can be a literal or another variable of the same data type.

Compound Assignment Operators

In C++, the assignment operator can be combined into a single operator with some other operators to perform a combination of two operations in one single statement. These operators are called Compound Assignment Operators. There are 10 compound assignment operators in C++:

Addition Assignment Operator ( += )
Subtraction Assignment Operator ( -= )
Multiplication Assignment Operator ( *= )
Division Assignment Operator ( /= )
Modulus Assignment Operator ( %= )
Bitwise AND Assignment Operator ( &= )
Bitwise OR Assignment Operator ( |= )
Bitwise XOR Assignment Operator ( ^= )
Left Shift Assignment Operator ( <<= )
Right Shift Assignment Operator ( >>= )

Lets see each of them in detail.

1. Addition Assignment Operator (+=)

In C++, the addition assignment operator (+=) combines the addition operation with the variable assignment allowing you to increment the value of variable by a specified expression in a concise and efficient way.

This above expression is equivalent to the expression:

2. Subtraction Assignment Operator (-=)

The subtraction assignment operator (-=) in C++ enables you to update the value of the variable by subtracting another value from it. This operator is especially useful when you need to perform subtraction and store the result back in the same variable.

3. Multiplication Assignment Operator (*=)

In C++, the multiplication assignment operator (*=) is used to update the value of the variable by multiplying it with another value.

4. Division Assignment Operator (/=)

The division assignment operator divides the variable on the left by the value on the right and assigns the result to the variable on the left.

5. Modulus Assignment Operator (%=)

The modulus assignment operator calculates the remainder when the variable on the left is divided by the value or variable on the right and assigns the result to the variable on the left.

6. Bitwise AND Assignment Operator (&=)

This operator performs a bitwise AND between the variable on the left and the value on the right and assigns the result to the variable on the left.

7. Bitwise OR Assignment Operator (|=)

The bitwise OR assignment operator performs a bitwise OR between the variable on the left and the value or variable on the right and assigns the result to the variable on the left.

8. Bitwise XOR Assignment Operator (^=)

The bitwise XOR assignment operator performs a bitwise XOR between the variable on the left and the value or variable on the right and assigns the result to the variable on the left.

9. Left Shift Assignment Operator (<<=)

The left shift assignment operator shifts the bits of the variable on the left to left by the number of positions specified on the right and assigns the result to the variable on the left.

10. Right Shift Assignment Operator (>>=)

The right shift assignment operator shifts the bits of the variable on the left to the right by a number of positions specified on the right and assigns the result to the variable on the left.

Also, it is important to note that all of the above operators can be overloaded for custom operations with user-defined data types to perform the operations we want.

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CS 2110: Object-Oriented Programming and Data Structures

Assignment 4: formula evaluation.

Programming languages give us as programmers the ability to evaluate mathematical expressions like a calculator, including expressions that involve variables. The language’s compiler translates the formula into instructions that a computer’s CPU can execute. But what if we want our program’s users to be able to type in their own expressions at runtime and have them be evaluated? Their formula will be user input (a String ), not source code, so we’ll need our program to evaluate it step-by-step with the help of appropriate data structures.

As an application, let’s once again consider spreadsheets. Some cells contain plain text or numbers, but other cells may specify a formula that should be used to compute its value, taking as input the values of other cells. For example, in Microsoft Excel, the formula =A1+B1 means that the cell’s value should be the sum of the values in row 1, columns A & B (see figure).

In this assignment, you will write an application that evaluates postfix formulas in spreadsheets saved in CSV format. Along the way you will develop an interactive calculator to help build intuition for the data structures involved. This project involves a lot of Java classes; some of them will be given to you (in which case you must study their specifications as a client ), while others you will develop from scratch. As usual, you will write JUnit test cases for all of your code, annotated with human-readable assertions of specifications.

Learning Objectives

Leverage subtype polymorphism to represent expression trees containing multiple kinds of nodes.
Process tree data structures recursively.
Report and respond to failed operations using exceptions.
Write tests (using lambdas) that expect exceptions to be thrown.
Use classes from a third-party library.

Recommended schedule

Start early. This is a big assignment! Office hours and consulting hours are significantly quieter shortly after an assignment is released than closer to the deadline. We recommend spreading your work over at least 5 days. Here is an example of what that schedule could be:

Day 1: Read this handout and open the project in IntelliJ. Confirm that the test suites compile and run. Part I—Test and implement eval() and opCount() for all Expression classes. Write “stubs” for all other Expression methods so that your code compiles and your tests can run.
Day 2: Part I continued—Test and implement infixString() and postfixString() for all Expression classes. Then test and implement equals() (which will come in handy for future tests).
Day 3: Part II—Test and implement RpnParser , then perform further testing by using RpnCalc to interact with your expression trees.
Day 4: Part III—Return to your Expression classes and test and implement dependencies() and optimize() . Use RpnCalc to see this functionality in action.
Day 5: Part IV—Implement CsvEvaluator . Test it both with the provided unit tests and with the provided CSV files. Try creating and evaluating a few spreadsheets of your own.

Note that this schedule does not include the challenge extensions. If you plan on tackling these, be sure to leave an extra couple of days at the end of your schedule.

Collaboration policy

On this assignment you may work together with one partner. Having a partner is not needed to complete the assignment: it is definitely do-able by one person. Nonetheless, working with another person is useful because it gives you a chance to bounce ideas off each other and to get their help with fixing faults in your shared code. If you do intend to work with a partner, you must review the syllabus policies pertaining to partners under “programming assignments” and “academic integrity.”

Partnerships must be declared by forming a group on CMSX before starting work. The deadline to form a CMS partnership is Friday, March 22 . After that, CMSX will not allow you to form new partnerships on your own. You may still email your section TA (CCing your partner) to form a group late, but a 5 point penalty will be applied. This is to make sure you are working with your partner on the entire assignment, as required by the syllabus, rather than joining forces part way through.

As before, you may talk with others besides your partner to discuss Java syntax, debugging tips, or navigating the IntelliJ IDE, but you should refrain from discussing algorithms that might be used to solve the problems, and you must never show your in-progress or completed code to another student who is not your partner. Consulting hours are the best way to get individualized assistance at the source code level.

Frequently asked questions

Note: This assignment includes some “challenge extensions” that are worth very few points but will provide a lot of additional practice for students who choose to tackle them. Do not feel discouraged if you don’t have time to try these challenges—you can still earn an ‘A’ grade without attempting them at all. If you do attempt them, course staff will only be able to provide limited debugging assistance.

If needed, there will be a pinned post on Ed where we will collect any clarifications for this assignment. Please review it before asking a new question in case your concern has already been addressed. You should also review the FAQ before submitting to see whether there are any new ideas that might help you improve your solution.

Remember that the student handbook outlines requirements that apply to all assignments in this course. Please ensure that your submission complies with these to avoid deductions during grading.

Assignment overview

For this assignment you will be creating three Java classes from scratch (representing polymorphic expression tree nodes) and completing two applications: an interactive calculator and a spreadsheet formula evaluator .

Make sure to open the “a4” folder as a project in IntelliJ following the procedure from previous assignments (this is extra important for this assignment, as it depends on a third-party library in the “lib” folder). If IntelliJ complains about standard Java classes, try “File | Repair IDE” and advance it through “step 3”. Here is a brief tour of what you’ll find inside your project:

Whew! Your programs are getting bigger! Fortunately, you only need to worry about submitting 4 of these files (plus 3 new ones you will create).

Note that achieving reasonable coverage of the expression classes requires a lot of test cases. But each one only needs a couple lines of code, and we have provided English descriptions of the cases that you need.

Part I: Expression nodes

Expression trees.

As discussed in lecture 14, a tree is a natural data structure for representing mathematical expressions, since operands and function arguments are themselves subexpressions. Consider the expression $2 \cdot (y - 1) + 3$. The operands to the multiplication operator are the constant $2$ and the subexpression $(y - 1)$. And the whole subexpression $2 \cdot (y - 1)$ serves as the first operand to the addition operator. These hierarchical relationships form a tree as shown in the figure, which each node containing either a constant, a variable, or an operator.

Expressions are evaluated recursively: an operator node recursively evaluates its left operand, then its right operand, and then combines those returned values to produce its result. An operator always has two children (its left and right operands), but in this assignment we will also support function nodes, like sin() and cos() , that have a single child (their argument subexpression).

To review mathematical expressions and their representation as trees, see the following textbook sections:

Segment 5.5 (Using a Stack to Process Algebraic Expressions), focusing on 5.17–5.18
Chapter 24, 24.22–24.24 (Expression Trees)

Reverse Polish notation (RPN)

We are used to writing mathematical expressions in “infix” notation, like 2*(y - 1) + 3 . However, this notation requires knowing the precedence of each operator (e.g., multiplication/division before addition/subtraction), and parentheses are often required to achieve the desired order of operations. Parsing such expressions in software is, consequently, a little tricky. But there is another way to write expressions that never requires parentheses, corresponding to a postorder traversal of the corresponding expression tree. This is called “postfix notation,” a.k.a. “reverse Polish notation” (RPN).

As an example, the previous expression would be written in RPN as 2 y 1 - * 3 + . For this assignment, all formulas typed into your calculator or saved in spreadsheets will be in reverse Polish notation.

Here are some correspondences between our infix and RPN notations:

Note that, to eliminate any possibility of ambiguity, every binary operation is enclosed in parentheses in our infix notation.

Our Expression interface

Our expression trees will be composed of polymorphic nodes implementing the Expression interface. This means that each node could have a different class, each one specializing Expression in a particular way (i.e., constant numbers vs. binary operators). For example, the expression $1 - 2 \sin^2(y / 2)$ would be represented by the following tree, where “C” indicates a Constant node, “V” indicates a Variable node, “A” indicates an Application node, and “O” indicates an Operation node:

Here is a class diagram showing the methods required by Expression and the fields of the concrete classes that you’ll be writing:

Expressions can be evaluated, they can count how many operations are required to evaluate them, and they can write themselves in infix or postfix notation. Read the specifications in “Expression.java” for the specifics.

The Constant class has been written for you. It represents a single number, stored in its value field.

Define public classes Variable , Application , and Operation implementing the Expression interface in new corresponding “.java” files. Start by creating “stubs” for each of the required methods (IntelliJ can do this for you; see below). Declare the fields that will represent each class’s state according to the class diagram above, then define constructors to initialize those fields. (You may order your constructor parameters however you like, so long as their interpretation is clear from their specifications. There is a small advantage to following the order of the fields in the diagram above, as that will match some test templates we provide to you.)

You can choose whether to implement all the methods in one class before moving on to the next one, or whether to implement one method at a time across all of the classes. We recommend the latter, as it will enable you to test each operation on arbitrary expressions as you go.

Here is a brief overview of these three classes. These descriptions should be enough for you to write specialized specifications for eval() , opCount() , infixString() , postfixString() , and equals() in each class. The remaining operations will be discussed later.

Variable nodes

These represent a named variable (like $y$) in an expression; their state is simply the variable’s name. Variables are useful because they allow us to write down an expression without yet knowing the values of all of the terms. For example, in our spreadsheet formulas, variables with names like “B1” will refer to values in other cells of the spreadsheet. To evaluate expressions containing variables, a client must pass in a VarTable containing the values of those variables.

Like constants, variable nodes are leaf nodes and have no children. When evaluated, they return the value of their variable (if it exists in the VarTable ), or else they throw an UnboundVariableException . We do not consider this lookup to be an “operation” as counted by opCount() . When a variable is written as a string, a variable is simply represented by its name, regardless of notation (infix vs. postfix).

Since variable nodes are leaves, two of them are equal if they represent the same variable name.

Application nodes

These represent the application of a function to an argument ; the argument can be any non-empty subexpression. For example, the expression $\sin(y / 2)$ expresses the application of the $\sin()$ function to the subexpression $y / 2$. The argument is stored as a single child Expression node. The function to call is an instance of our UnaryFunction class, which can be evaluated on a numeric argument by calling its apply() method. UnaryFunction can also report its name so we know how to identify the function in a string.

To evaluate an Application node, it should evaluate its argument child, then apply its function to that value and return the result. Calling its function counts as one “operation”. In infix notation, an Application is represented by the name of its function, followed by the infix representation of its argument, enclosed in parentheses. For example, the expression above would be written as "sin((y / 2))" (note the double parentheses—one pair for the function application, and one pair for the Operation argument, to be discussed next). In postfix notation, an Application is represented by its argument’s postfix string, followed by the function name with a "()" suffix (this is to distinguish functions from variables). E.g., "y 2 / sin()" .

Two Application nodes are equal if their functions and arguments are equal.

Operation nodes

These represent the binary operators common in arithmetic: addition ( + ), subtraction ( - ), multiplication ( * ), division ( / ), and exponentiation ( ^ ). Their operands are stored as two child Expression nodes, distinguishing between left and right (since subtraction, division, and exponentiation are not commutative). The operator is an instance of our Operator class, which can be evaluated on numeric operands by calling its operate() method. Operator can also report its symbol so we know how to identify it in a string.

To evaluate an Operation node, it should evaluate both of its operand children, then combine those value with its operator and return the result. This counts as one “operation”. In infix notation, an Operation is always enclosed in parentheses, and its operands are separated from its operator symbol by spaces. What we would write mathematically as $(2 y + 1)^3$ should be expressed as the string "(((2 * y) + 1) ^ 3)" . To express an Operation in postfix notation, simply perform a postorder traversal, as discussed in lecture for binary trees. The same expression in postfix notation would be "2 y * 1 + 3 ^" .

Two Operation nodes are equal if their operator and operands are equal.

Note: you should not need to do any dynamic type queries (i.e., instanceof , getClass() , casting) when implementing the behavior of the various expression nodes (other than in equals() , where our usual template is fine). Nor should you need to write any loops. Rely on recursion and subtype polymorphism and trust your child nodes to do the right thing.

Testing expressions

“ExpressionTest.java” declares nearly 50 unit tests for the various Expression classes. About half of the tests have been implemented for you, while you are responsible for implementing the remaining ones. As usual, we strongly recommend implementing (or uncommenting) the tests related to the behavior you are about to implement. Writing (or reading) the test case will clarify the function’s specification for you, and seeing the case change from “fail” to “pass” provides a reward when your method implementation is on the right track. And if a test doesn’t turn green, you know exactly which code must be at fault.

Each case is annotated with a @DisplayName() that describes the behavior being tested. The description gives the context, identifies the operation being performed, and specifies the expected result. It is hopefully clear how each case relates to the specifications of a class’s methods; occasionally these descriptions may even help clarify a dense specification.

For each case that says fail(); // TODO , you are responsible for replacing this stub with a test implementation that meets the criteria described by the @DisplayName() . You are encouraged to copy-paste portions of other tests to speed up this process as long as the result is consistent with the test description.

Some tests have already been implemented but have been commented out. This is because we did not specify the constructor signatures for your Expression classes. You must uncomment each of these cases and adjust the constructor invocations (if necessary) so that the tests run.

Despite the relatively large number of tests in this suite, it probably still does not provide 100% line coverage of your classes (though hopefully it covers at least 90%). Furthermore, it does not come close to testing all possible combinations of node types, operators, functions, and variable names. But writing clear specifications at the interface level, then testing that each component meets those specifications individually, is still critical for avoiding bugs when composing software modules in arbitrary ways like this.

Testing exceptions

Since some of the methods promise to throw an exception under certain conditions, you should include tests that check whether an exception is thrown as specified. The JUnit function assertThrows() is the right tool for the job, but it works a little differently than other JUnit assertions. You must specify the expected exception’s Class object, and you must defer execution of the exception-throwing code using an anonymous function .

Let’s take testEvalUnbound() in VariableExpressionTest as an example. When eval() is called on a Variable expression expr , we expect it to throw an UnboundVariableException if the variable’s name is not in the provided VarTable argument. This behavior is tested using the following code:

We’ll come back to anonymous functions in more detail later in the course, but for now you can use them in this idiomatic way by just putting () -> in front of expressions whose evaluation needs to be deferred.

Part II: Parsing RPN expressions

As you likely concluded from your testing, assembling expression trees from individual nodes is tedious. We need a way to parse a postfix expression string, provided by a user, and return the corresponding expression tree (this is basically the inverse of the postfixString() methods you implemented earlier). This is the job of RpnParser.parse() .

Implementing this parser is the most important part of the assignment. Since we didn’t dictate the order of constructor arguments for your Expression classes, the only way our autograder will be able to create expression nodes is by parsing expression strings using your RpnParser . It will also probably be the longest method you write for this assignment.

Given an expression in RPN, you build the expression tree from the bottom up using the following procedure:

Initialize a Stack of expression nodes.
If the token is a number or a variable name, push a corresponding leaf node onto the stack.
If the token is an operator or a function name, pop the appropriate number of operands/arguments off of the stack, construct a new interior node with the operation and arguments, and push the new node onto the stack.
Assuming the expression is valid, there will be one node left on the stack. This is the root of the expression tree.

Playing with an RPN calculator can help build your intuition for this procedure.

In RpnParser.parse() , we start you off with a few key elements: an empty stack of Expression nodes and an iteration over Token s. The tokens are created by splitting the expression string at whitespace, then determining whether each substring is a number, an operator, a function call (ending in "()" ), or a variable name (any other string). Each token will therefore be one of the following subclasses of Token (the Token. prefix just indicates that they were defined as nested classes in the same file):

Token.Number
Token.Operator (note: this is not the same class as Operator )
Token.Function
Token.Variable

As described by the TODO, you should query the dynamic type of each token yielded by the iteration (using instanceof ), then take the appropriate action for each kind. If you ever need to pop more expressions off the stack than are available, you should throw IncompleteRpnException ; likewise if, at the end of the procedure, there is not exactly one Expression remaining. Note that each subclass of Token defines some useful behavior, accessible via appropriate casting. For example, a Token.Operator can give you its corresponding Operator object via opValue() . Functions, however, must be looked up from the funcDefs argument provided by the client (this is to support user-defined functions , one of the challenge extensions).

Implement your parser , then test it against the cases in RpnParserTest . Note that this testing is deliberately incomplete. Heed the advice in the comments add additional test cases to ensure that your parser is working as expected. There are plenty of examples of postfix expressions in this handout that you can use.

Part III: Calculator functionality

Once your parser is implemented, you can interact with your expressions using the RpnCalc calculator app. This calculator has already been implemented (except for a few advanced functions left as challenges), so go ahead and run it and type help to see the commands that are available. The calculator remembers the last expression that was entered, so if you do not provide a new expression with each command, it will reuse the old one (the square brackets around [<expr>] in the help message indicate that the argument is optional).

Type eval 2 1 1 0 + + + to evaluate $2 + 1 + 1 + 0$. Type infix to print the expression in infix notation. Type opcount to count the number of operations needed to evaluate it. To exercise variables and functions, try set pi 3.1415926535897932 , then eval pi 2 / sin() .

The file “calc-commands.txt” contains another sequence of calculator commands. To run them all at once, you can pass the filename as a program argument to RpnCalc . However, it will crash when trying to run the deps and optimize commands if you still have stubs in your expression classes. Let’s fix that.

Variable dependencies

If a formula gets very long, it might be handy to know all of the variables it depends on. Since the same variable may appear in multiple subexpressions, a Set of variable names is the appropriate ADT to represent this information (so duplicates are not repeated).

Implement the dependencies() method in all of your Expression classes. A Variable node depends on itself. All other nodes interior nodes depend on the union of their children’s dependencies (this is all you need to know to document the refined specs for each class). Your implementation must be recursive and, as before, should not do any runtime type checking on Expression s. You are allowed to use Set , HashSet , and/or TreeSet from java.util to implement this. Be aware that the convenient Set.of() methods produce unmodifiable sets, so if you need to add more elements, you’ll need to construct a new set of a concrete class that you can add to.

Optimization

If a formula contains a lot of operations, it can be expensive to evaluate it over and over again (as you might do when graphing a function, for example). But if a subexpression only depends on constants or variables whose values are known and fixed, then the value of that subexpression won’t change with repeat evaluations. Therefore, we can replace the subtree representing that subexpression with a constant node to avoid having to recompute the operations. This is an optimization known as constant folding .

Implement the optimize() method in all of your Expression classes. A Variable can only be optimized if it has an assigned value in the provided variable table, in which case it optimizes to a Constant ; otherwise, it optimizes to itself. An Application or Operation node can be fully optimized to a Constant if its children can all be evaluated to yield a number. But even if a child subtree depends on an unbound variable, the parent node can still be partially optimized by creating a new copy whose children are replaced with their optimized forms. These rules should be sufficient for you to document the refined specs for each class. If you have any doubts about the expected behavior, take a look at the test cases.

As an example, optimizing the expression $(x + 2 \cdot 3) / (y - 1)$ when $y$ is assigned the value $2$ yields the simpler expression $(x + 6)/1$:

Assignment metadata

You’ve made great progress! At this point, you can fill in some of the fields in “reflection.txt”. Enter your name and NetID (both partners if working in a group), then answer the verification questions using RpnCalc .

Part IV: Spreadsheet evaluator

Now that you have a working RPN expression evaluator, let’s put it to work evaluating spreadsheet formulas. The CsvEvaluator application should read the rows and columns of a spreadsheet saved in a CSV file and copy them in CSV format to System.out . But when it encounters a cell whose value starts with an equals sign, = , it should parse the remainder of that cell’s value as an RPN formula, evaluate it, and print that value instead. If the formula cannot be evaluated for any reason, it should be replaced by #N/A in the output.

A spreadsheet formula may refer to values in other cells by using their column–row coordinates as variables in the expression. For example, the formula in the Excel screenshot at the start of this handout would be written as =A1 B1 + , where A1 refers to the cell in the first column (A) of the first row, while B1 refers to the cell in the second column (B) of the first row. Formulas may refer to cells containing either numbers or other formulas, but for simplicity, a formula may only refer to cells on previous rows or cells on the same row but in previous columns (lifting this restriction requires computing a “topological ordering” of formulas, which you will learn how to do later in the course).

Here is an example of the program’s input and output, shown as tables (the row and column headers would not be included in the CSV output):

The main() method of CsvEvaluator has been written for you. Your task is to implement evaluateCsv() according to its specifications. But in order to do so, you’ll first want a helper function to convert between column numbers and column letters.

Column labels

Traditionally, spreadsheet columns are labeled by letters, rather than numbers. The first column is labeled ‘A’, the second column is labeled ‘B’, etc. If more than 26 columns are used, a second letter is added: ‘AA’ is 27, ‘AB’ is 28, and so on. To convert a column position into its label, we need to represent the number in this base-26 numeral system. But because there is no letter corresponding to 0, the process is a little bit different.

Expressing integers in different bases is a classic (exam) problem with a recursive solution. First, the number $n$ is divided by the base $b$, yielding an integer quotient $q$ and a remainder $r$. These obey the relationship $n = q b + r$, subject to $0 \leq r \leq b-1$. The ones digit of the representation is then the remainder $r$, and the rest of the digits are simply the base-$b$ representation of the quotient, $q$. The base case is when the quotient is 0, in which case no more digits should be written to the left.

But the column labeling scheme is what’s known as a “ bijective numeral system ”, which do not use a 0 digit (the number 0 itself is written as the empty string). The algorithm is very similar to that for positional notation, except that the “quotient” $q^\prime$ is defined slightly differently: it is the largest integer that, when multiplied by the base $b$, is strictly less than $n$ (recall that a normal quotient is the largest integer that, when multiplied by $b$, is less than or equal to $n$). The relationship between the quotient and remainder is the same as before, meaning that now $1 \leq r^\prime \leq b$.

With this in mind, implement colToLetters() to recursively convert column positions to labels. Note that this will require converting integers to characters; thankfully, Latin letters in alphabetical order correspond to consecutive integers in Unicode. Therefore, to find, e.g., the 5th letter in the alphabet (which is 4 letters after ‘A’), one can write (char)('A' + 4) .

Working with CSV files

As mentioned in A3, writing a robust parser for CSV files requires a lot of attention to detail in order to accommodate strings that contain commas or newlines. Rather than reinventing the wheel, we should take advantage of solutions that other programmers have already written and tested. To do so, this assignment includes a third-party dependency , a free and open-source class library named “ Apache Commons CSV ”.

CsvEvaluator has already done the work of setting up this library and creating a CSVParser to read the user’s input file and a CSVPrinter to print a CSV file to the console. Your solution will need to iterate over the rows and cells of the input (each row is an instance of CSVRecord ) and print rows of cells to the printer.

While you may use any of the methods provided by these classes, the following ones are sufficient to get the job done:

Note that, unlike in A3, there is no need to read the whole file into a list-of-lists or equivalent data structure. Since formulas can only depend on previous cells, you can write each cell as soon as you have read it. This approach is known as “ online ” processing.

The included CsvEvaluatorTest provides reasonably good coverage of both colToLetters() and evaluateCsv() . It also comments on cases that are known to not be covered by these tests. It is up to you to determine which of these situations might pose a risk to your implementation and to add additional tests as appropriate. You do not need to submit these tests, but that does not make them any less essential to confidently delivering a working solution.

For an end-to-end test of the whole application, try running it with the program argument “pizza.csv”. The output should match the contents in “pizza-out.csv”.

Part V: Challenge extensions

The last few points of the assignment are reserved for challenge tasks. These require a significant amount of effort for relatively few points and are intended as additional exercise for students who complete the rest of the assignment ahead of schedule. It is okay to attempt none of the challenge tasks ; they are not included in the recommended schedule. If you do not want to attempt a challenge, there is no need to upload the corresponding file.

Alternative VarTable implementation (3 points)

You have used the MapVarTable class when writing test cases for expression nodes and when implementing the calculator and spreadsheet evaluator. As its name suggests, it is implemented using a Java HashMap . But the methods in Expression accept any implementation of the VarTable interface, meaning you can use an alternative class instead.

Implement a class named TreeVarTable that implements the VarTable interface using a binary search tree data structure (see Chapter 26). All related code must go in the file “TreeVarTable.java” and must be appropriately documented. You must implement your own tree from scratch (using Java’s TreeMap does not qualify, nor may you copy-paste the textbook or lecture demo implementations). Be sure to test your class thoroughly with a JUnit test suite (which you do not need to submit). Your class must have a default constructor that yields an empty map.

You may use your TreeVarTable class instead of MapVarTable throughout the rest of the assignment (as a form of end-to-end testing), but we do not necessarily recommend submitting this, as any bugs in your TreeVarTable would then count against the code that depends on it.

Additional calculator functionality (2 points)

Implement the following additional features in RpnCalc , replacing their corresponding TODOs:

tabulate <var> <lo> <hi> <n> [<expr>] : Evaluate the current expression ( expr if provided, otherwise the previously set expression) n times, varying the value of variable var between lo and hi . Print a line for each evaluation containing the current value of var followed by the value of the expression.

Example—tabulate the expression $x^2$ for $x$ in the range of 0 to 4:

After executing this command, var should have the value hi .

def <name> <var> [<expr>] : Define a new function named name that will evaluate the current expression ( expr if provided, otherwise the previously set expression) with variable var set to the function’s argument. This function can then be used in future expressions. Unlike variables, functions may not be redefined (attempting to do so is a user error and should be reported as such). Additionally, an expression used to define a function may not depend on any variables other than var (the def command handler should check this).

Example—define a function sqr() that squares its argument, then use it in an expression:

If the user makes an error in invoking one of these commands, your command handler should print a helpful error message to System.err and return (it should not propagate any exceptions). Note that Scanner ’s exceptions are unchecked, so you’ll need to study its documentation to know what to catch.

Return to “reflection.txt”, estimate the amount of time you spent on this assignment, and answer the reflection question. Then submit the following files:

Variable.java
Application.java
Operation.java
ExpressionTest.java
RpnParser.java
CsvEvaluator.java
reflection.txt
RpnCalc.java (no need to submit if not attempting challenge extension)
TreeVarTable.java (no need to submit if not attempting challenge extension)

You hopefully wrote additional test cases for RpnParser and CsvEvaluator to improve your confidence in your solution, but those tests will not be submitted.

Smoketesting

The smoketester will check the following:

Your Expression classes, ExpressionTest suite, and RpnParser will be compiled together, since constructors are not part of the Expression interface.
Does your ExpressionTest suite pass when used to test your own implementations of the Expression classes?
Does your RpnParser pass the test cases included in the release code?
What is the output of RpnCalc when executing the commands in “calc-commands.txt”?
Does your CsvEvaluator pass the test cases included in the release code?
What is the output of CsvEvaluator when evaluating “pizza.csv”, and does it differ from “pizza-out.csv”?

When it comes time to grade your submission, the autograder will additionally check at least the following:

Do your implementations of the Expression classes, as created by RpnParser , pass our full test suite?
Do your RpnParser , RpnCalc , and CsvEvaluator pass our full test suites?
Do your challenge extensions pass our corresponding test suites?

As usual, manual grading will check for compliance with implementation constraints as well as adherence to good coding style.

Property Appraiser 1 – 24140726

March 18, 2024

This position resides in the Property Assessment Division of the Department of Revenue . Duties include residential property reviews, discoveries, data research, and field appraisals. Complete inspections to determine the residential property final valuation. Analyze, assess, and classify land uses. Assist with specification, calibration, and benchmarking of land models, sales comparisons, and property characteristics. Support ongoing program operations and activities. Respond to taxpayer inquiries and explain appraisal activities. Provide dispute resolution and participate in appeal hearings. The position does not supervise other staff.

Key Responsibilities Include:

Conduct property reviews and discoveries to identify appraisal needs and priorities, recommend priorities based on property use, value, location, and other characteristics.
Review tax records, land use, improvements, valuation documents, and other information.
Identify properties for appraisal review.
Research and analyze individual residential property characteristics to estimate the impact on property values.
Analyze and evaluate appraisal information and determine final property value.
Examine site and improvement data, sanitation regulations, zoning, planning, covenants, deed restrictions, and other technical and legal documentation.
Compile and analyze construction cost data and determine the effects on property values.
Conduct field appraisals and site inspections of subject properties.
Perform comparable sales to identify valuation factors.
Collect data required for maps, plats, and sketches used in appraisals.
Determine the primary use for appraised properties.
Document professional assumptions and limiting conditions.
Determine comparable sales data and adjustments to valuations.
Estimate the value of site improvements.
Determine appropriate appraisal method (cost or market) for residential properties.
Verify information in title and ownership data, inspection reports, market models, and other sources.

Working Conditions

Work hours may exceed 40 hours from time to time, including weekends.
Office environment.
Working outside.
Lifting is infrequent, less than 15 pounds.
Travel is required, must have a valid driver’s license.

Knowledge of:

Appraisal methods for residential properties
Construction, mapping, GIS, and cadastral
Property sales and valuations procedures
Research and analysis
Accuracy and attention to detail
Conflict resolution
Microsoft programs and other data base applications
Written, verbal, and interpersonal communication

You would be a great fit for this position if you have:

Self-motivation
Follow instructions
Provide timely customer service
Multitask and prioritize work under deadlines
Basic computer skills
Conflict Resolution
Ability to communicate with a wide range of personalities using discretion, active listening, critical thinking, and problem sensitivity.
Written and verbal communication
Outstanding Customer Service

(All computer systems and tax guidelines will be trained on the job.)

REMOTE/TELEWORK: This position may be eligible to work from an approved worksite within the state of Montana. This position would be required to report to a Department of Revenue office assigned by the supervisor. Employees must meet and sustain Department of Revenue telework eligibility requirements and supervisor's approval to participate in the DOR Telework Program.

Training Assignment: This agency may use a training assignment. Employees in training assignments may be paid below the base pay established by the agency pay rules. Conditions of the training assignment will be stated in writing at the time of hire.

Successful applicants are required to successfully pass DOR tax and background check(s).

*This is an incomplete list of job duties. For a complete job description please contact Human Resources at [email protected] or (406) 444-9858.

To be considered for a Department of Revenue position, successful applicants are required to successfully pass tax compliance and criminal background check(s). DOR is an equal opportunity employer. Women, minorities, and people with disabilities are encouraged to apply.

Education and Experience

The above competencies are typically acquired through a combination of education and experience equivalent to:

Two years of post-secondary education in business, accounting, economics, public administration, construction technology or training; and
One year of job-related experience.
Preferred work experience includes appraisal, property tax appraisal, assessment, auditing, agriculture, forestry, surveying, real estate, or related field.
Requires Montana certification in residential property appraisal (IAAO 101), per ARM 42.18.206-208 and MCA Title 15; within the first year of employment.

Other combinations of education and experience will be evaluated on an individual basis.

*If you have documented postsecondary education, please attach your transcripts to your application for it to be considered in the evaluation process.

Applicant Pool Statement

If another department vacancy occurs in this job title within six months, the same applicant pool may be used for the selection.

Training Assignment Available

This agency may use a training assignment. Employees in training assignments may be paid below the base pay established by the agency pay rules. Conditions of the training assignment will be stated in writing at the time of hire.

Job Overview

Apply For This Position

The Education Donations Portal 2.0 is Now Available!

You may now register to receive donations as a Montana Public School District or Student Scholarship Organization.

For more information on tax credits for qualified education contributions, please see our guide .

Citizen Services Call Center

We’re available Monday through Thursday, 9:00 a.m. until 4:00 pm. and Friday, 9:00 a.m. until 1:00 p.m.

Taxpayer Advocate

If you need help working with the department or figuring out our audit, appeals, or relief processes, the Taxpayer Advocate can help.

Payment and Filing Options

Payment options, filing options.

The Department of Revenue works hard to ensure we process everyone’s return as securely and quickly as possible.

Unfortunately, it can take up to 90 days to issue your refund and we may need to ask you to verify your return .

We encourage all Montanans to file early and electronically. This is the easiest and most secure way to file and get your refund as quickly as possible.

Remember, we are here to help. Please contact us if you need additional assistance.

Where's My Refund?

The My Revenue portal will no longer be available after July 23, 2021. Department of Revenue forms will be made available on MTRevenue.gov.

If you have records currently saved in My Revenue, we ask you to log into your My Revenue account and download them before July 23, 2021.

Log into My Revenue

We understand COVID-19 impacts all aspects of our community. Throughout this event, we will work hard to keep you updated on the impact COVID-19 has on taxation, alcoholic beverage control, and property assessment.

We serve the people of Montana and are here to help you through this time of crisis.

If you have been impacted by COVID-19 and are facing hardships, we will work with you to find a solution.

To see how other agencies have been impacted by COVID-19 go to COVID19.mt.gov .

We are continually reviewing due dates and deadlines. Please check back regularly or subscribe for COVID-19 updates to receive notifications for future changes.

Information Regarding COVID-19 Stimulus Payments

Stimulus payments are being issued by the IRS.

The Montana Department of Revenue is unable to assist in securing your stimulus payment.

You can check on the status of your COVID-19 Stimulus payment at IRS.gov/Coronavirus/Get-My-Payment .

Subscribe for Updates on COVID-19’s Impact to the Department of Revenue

Other COVID-19 Resources

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This operator first adds the current value of the variable on left to the value on the right and then assigns the result to the variable on the left. Example: (a += b) can be written as (a = a + b) If initially value stored in a is 5. Then (a += 6) = 11. 3. "-=" This operator is combination of '-' and '=' operators.
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C provides an assignment operator for this purpose, assigning the value to a variable using assignment operator is known as an assignment statement in C. The function of this operator is to assign the values or values in variables on right hand side of an expression to variables on the left hand side. The syntax of the assignment expression
What are Assignment Statement: Definition, Assignment Statement ...
Built-in Data Types. An Assignment statement is a statement that is used to set a value to the variable name in a program. Assignment statement allows a variable to hold different types of values during its program lifespan. Another way of understanding an assignment statement is, it stores a value in the memory location which is denoted.
Assignment Expressions (GNU C Language Manual)
7 Assignment Expressions. As a general concept in programming, an assignment is a construct that stores a new value into a place where values can be stored—for instance, in a variable. Such places are called lvalues (see Lvalues) because they are locations that hold a value. An assignment in C is an expression because it has a value; we call it an assignment expression.
Assignment Operators in C
In C, the assignment operator stores a certain value in an already declared variable. A variable in C can be assigned the value in the form of a literal, another variable or an expression. The value to be assigned forms the right hand operand, whereas the variable to be assigned should be the operand to the left of = symbol, which is defined as ...
Assignment Operators in C Example
The Assignment operators in C are some of the Programming operators that are useful for assigning the values to the declared variables. Equals (=) operator is the most commonly used assignment operator. For example: int i = 10; The below table displays all the assignment operators present in C Programming with an example. C Assignment Operators.
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The rule is to return the right-hand operand of = converted to the type of the variable which is assigned to. int a; float b; a = b = 4.5; // 4.5 is a double, it gets converted to float and stored into b. // this returns a float which is converted to an int and stored in a. // the whole expression returns an int. Share.
C Assignment Operators
Syntax. The assignment operators in C can both transform and assign values in a single operation. C provides the following assignment operators: In assignment, the type of the right-hand value is converted to the type of the left-hand value, and the value is stored in the left operand after the assignment has taken place. The left operand must ...
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for assignments to class type objects, the right operand could be an initializer list only when the assignment is defined by a user-defined assignment operator. removed user-defined assignment constraint. CWG 1538. C++11. E1 ={E2} was equivalent to E1 = T(E2) ( T is the type of E1 ), this introduced a C-style cast. it is equivalent to E1 = T{E2}
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Declaration: int a; Assignment: a = 3; Declaration and assignment in one statement: int a = 3; Declaration says, "I'm going to use a variable named "a" to store an integer value."Assignment says, "Put the value 3 into the variable a." (As @delnan points out, my last example is technically initialization, since you're specifying what value the variable starts with, rather than changing the value.
Assignment operators
Assignment performs implicit conversion from the value of rhs to the type of lhs and then replaces the value in the object designated by lhs with the converted value of rhs . Assignment also returns the same value as what was stored in lhs (so that expressions such as a = b = c are possible). The value category of the assignment operator is non ...
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1.Simple Assignment or Basic Form: Simple Assignment or Basic form is one of the common forms of Assignment Statements in C program. Simple Assignment allow the programmer to declare,define and initialize and assign a value in the same statement to a variable. This form is generally used when the programmer want to use the Variable a few times.
What is the result of an assignment expression in C?
Assignment returns with the assigned value. In case c=10 is 10. Since 10!=0, in c it means also true so this is an infinite loop. It is like you would write. while(10) Plus You've made the assignment. If You follow this logic, You can see, that. while(c=0) would be a loop that never executes its statement or block.
Assignment and shorthand assignment operator in C
Shorthand assignment operator combines one of the arithmetic or bitwise operators with assignment operator. For example, consider following C statements. int a = 5; a = a + 2; The above expression a = a + 2 is equivalent to a += 2. Similarly, there are many shorthand assignment operators. Below is a list of shorthand assignment operators in C.
Assignment statements in C/C++
Assignment statement in C/C++: The assignment statement is used to assign a value (computed from an expression) to a variable Syntax:
Assignment Operator in C
Here is a list of the assignment operators that you can find in the C language: Simple assignment operator (=): This is the basic assignment operator, which assigns the value on the right-hand side to the variable on the left-hand side. Example: int x = 10; // Assigns the value 10 to the variable "x". Addition assignment operator (+=): This ...
CUED
4. Assignment of variables Assignment of statements. It is essential that every variable in a program is given a value explicitly before any attempt is made to use it. It is also very important that the value assigned is of the correct type. The most common form of statement in a program uses the assignment operator, =, and either an expression or a constant to assign a value to a variable:
Assignment Operators In C++
In C++, the assignment operator can be combined into a single operator with some other operators to perform a combination of two operations in one single statement. These operators are called Compound Assignment Operators. There are 10 compound assignment operators in C++: Addition Assignment Operator ( += ) Subtraction Assignment Operator ...
Assignment Operator in C
Assignment Operator in C is a tutorial that explains how to use the operator that assigns a value to a variable in C programming language. It covers the syntax, types, and examples of assignment operator in C. It also provides a quiz and interview questions to test your knowledge. Learn assignment operator in C from javatpoint, a leading online platform for learning various technologies.
Assignment 4: Formula evaluation (CS 2110 Spring 2024)
Assignment 4: Formula evaluation. Programming languages give us as programmers the ability to evaluate mathematical expressions like a calculator, including expressions that involve variables. The language's compiler translates the formula into instructions that a computer's CPU can execute.
c
So it is an assignment statement and has a return value in addition, equal to the value it assigned. That returned value (rvalue) is what is being assigned to sample1. - Hazem. ... In C++ assignment evaluates to an lvalue, which requires "chained" assignments to be sequenced.)
Property Appraiser 1
Applicant Pool Statement. If another department vacancy occurs in this job title within six months, the same applicant pool may be used for the selection. Training Assignment Available. This agency may use a training assignment. Employees in training assignments may be paid below the base pay established by the agency pay rules.
c++
The issue isn't with your answer - I think it's about the best possible factual discussion of the history of the "assignment in an if-statement" style came about. The problem is your answer was referred by someone who utterly missed your characterization of GCC's hack and actually used your answer as a defense of that hack. I was pointing out ...

Assignment Statement in C

The syntax of the assignment expression

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Tuple Assignment

Sequence Assignment

Multiple-target Assignment or Chain Assignment

Augmented Assignment

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7 Assignment Expressions

Assignment Operators in C

Simple assignment operator (=)

Augmented assignment operators

C Assignment Operators

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cppreference.com

[ edit ] Simple assignment

[ edit ] Notes

[ edit ] Compound assignment

[ edit ] References

[ edit ] See Also

[ edit ] See also

Assignment Statement (=) in C Language

Syntax :1.Basic Assignment statement

Naming Rules or conventions for Assignment Statement

Example 1: C program to illustrates the use of Simple Assignment statement .

2. Assignment Operator complete C Program.

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What is Assignment Operator in C language?

Example of Assignment Operator in C

Types of Assignment Operators in C

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Assignment Operators In C++

Compound Assignment Operators

1. Addition Assignment Operator (+=)

2. Subtraction Assignment Operator (-=)

3. Multiplication Assignment Operator (*=)

4. Division Assignment Operator (/=)

5. Modulus Assignment Operator (%=)

6. Bitwise AND Assignment Operator (&=)

7. Bitwise OR Assignment Operator (|=)

8. Bitwise XOR Assignment Operator (^=)

9. Left Shift Assignment Operator (<<=)

10. Right Shift Assignment Operator (>>=)

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CS 2110: Object-Oriented Programming and Data Structures

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Assignment overview

Part I: Expression nodes

Reverse Polish notation (RPN)

Our Expression interface

Variable nodes

Application nodes

Operation nodes