C++ Operators CS242 COMPUTER PROGRAMMING T.Banan Al-Hadlaq

Content 2  C++ operators  Assignment operators  Arithmetic operators  Increment and decrement operators  Decision making operators (logical and relational)  Conditional operator  Precedence and associativity of operators  Common errors

Operators  Data connectors within expression or equation.  Concept related  Operand: data that operator connects and processes.  Resultant: answer when operation is completed. Operators types based on number of operands 3 1.Unary operators Have only one operand. May be prefix or postfix. e.g. ! Binary operators Have 2 operands Infix ( between two operands). e.g. + && == 3.Ternary operators Have three operands. e.g. ? :

Operators (cont.) 4 Operators Types based on their mission Assignment Relational and Equality ArithmeticLogical =, +=, -=, *=, /=, %=, =, ==,!= +, -, *, /, %, ++, -- AND(&&) OR( || ) NOT( ! ) AND(&&) OR( || ) NOT( ! )

Assignment operators  In C++ ( = ) is called the assignment operator. It is Binary operators.  Assignment statement takes the form below:  Expression is evaluated and its value is assigned to the variable on the left side.  Shorthand notation: varName = varName operator expression; It will be: varName operator = expression; 5 varName = expression; c = c + 3; c += 3; c = c + 3; c += 3; Example:

Assignment operators (cont.) 6

Arithmetic Operators  Arithmetic expressions appear in straight-line form.  Parentheses () are used to maintain priority of manipulation. 7

Arithmetic Operators Precedence  Operators in parentheses evaluated first.  Nested parentheses. E.g. ( a * ( b + c ) )  Operators in innermost pair first.  Multiplication, division, modulus applied next.  Operators applied from left to right.  Addition, subtraction applied last.  Operators applied from left to right. 8

Example  The statement is written in algebra as z = pr % q + w / (x – y)  How can we write and evaluate the previous statement in C++ ? z = p * r % q + w / (x - y);

Increment and Decrement Operators  Increase operator (++): increases by one the value stored in a variable.  Decrease operator (--): reduces by one the value stored in a variable.  Increment operator gives the same result of (c=c+1) or (c+=1)  Decrement operator gives the same result of (c=c-1) or (c-=1) 10

Increment and Decrement Operators (cont.) 11  In the case that the increase operator is used as a prefix (++a)  the value is increased before the result of the expression is evaluated.  In case that it is used as a postfix (a++)  the value stored in a is increased after being evaluated.

Examples 12 int x = -10, y; y = ++x; cout << “x = “ << x << endl; cout << “y = “ << y << endl; int x = -10, y; y = ++x; cout << “x = “ << x << endl; cout << “y = “ << y << endl; Example # 1 x = -9 y = -9 x = -9 y = -9 output # 1 int x = -10, y; y = x++; cout << “x = “ << x << endl; cout << “y = “ << y << endl; int x = -10, y; y = x++; cout << “x = “ << x << endl; cout << “y = “ << y << endl; Example # 2 x = -9 y = -10 x = -9 y = -10 output # 2

Relational and Equality Operators  Binary operators  Used in decision -making statements 13

Relational and Equality Operators (cont.)  Have the same level of precedence.  Applied from left to right.  Used with conditions.  Return the value true or false. 14

Logical Operators  Used to combine between multiple conditions.  && (logical AND)  true if both conditions are true gender==‘f’ && age >= 65  || (logical OR)  true if either of condition is true semesterAverage >= 90 || finalExam >= st condition2 nd condition

Logical Operators (cont.)  ! (logical NOT, logical negation)  Unary operator.  Returns true when its condition is false, and vice versa !( grade == maximumGrade ) Also can be written as grade != maximumGrade 16

Conditional operator ( ?: )  Ternary operator requires three operands  Condition  Value when condition is true  Value when condition is false  Syntax 17 Condition ? condition’s true value : condition’s false value

Examples Can be written as Can be written as.. ? 18 grade >= 60 ? cout<<“Passed” : cout<<“Failed”; Example # 1 cout = 60 ? “Passed” : “Failed”); int i = 1, j = 2, Max; Max = ( i > j ? i : j ); int i = 1, j = 2, Max; Max = ( i > j ? i : j ); Example # 2

Summary of Operator Precedence and Associativity 19

Boolean Data Type 20 bool test1,test2,test3 ; int x = 3, y = 6, z = 4 ; test1 = x > y ; // false test2 = !(x == y ); // true test3 = x < y && x < z ; // true test3 = test1 || test2 ; // true test2 = !test1; // true bool test1,test2,test3 ; int x = 3, y = 6, z = 4 ; test1 = x > y ; // false test2 = !(x == y ); // true test3 = x < y && x < z ; // true test3 = test1 || test2 ; // true test2 = !test1; // true Code # 1

Common Compilation Errors  Attempt to use % with non-integer operands.  Spaces between pair of symbols e.g. (==, !=, …etc).  Reversing order of pair of symbols e.g. =!.  Confusing between equality (==) and assignment operator (=). 21

Exercise What is the output of the following program? 1 #include 2 3 using namespace std; int main() 7 { 8 int a, b=3; a=b; a+=2; 9 10 cout << a << endl; return 0; } // end main 1 #include 2 3 using namespace std; int main() 7 { 8 int a, b=3; a=b; a+=2; 9 10 cout << a << endl; return 0; } // end main

Exercise  Convert the following algebraic expression to an arithmetic C++ expressions: Solution: M=(a+b+c+d+e)/5

Exercise  Evaluate the following C++ expression: y= a * x * x + b * x + c; Assume that : A=2 X=5 B=3 C=7. Solution: y=2*5*5+3*5+7 y=10*5 +3*5 +7 y=50+3*5+7 y= y=65+7 y=72

Exercise  Write a program that calculates the average of two entered real numbers. The output will be:

Exercise