lect31 operators expressions

8/13/2019 Lect31 Operators Expressions

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COMPUTERPROGRAMMING I

(TA C162)

Lecture 31 Operators & Expressions


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Todays Agenda Operators and Expressions

Relational O erators Lo ical O erators

Assignment Operators Increment and Decrement Operators

Bitwise Operators, Special Operators

Control Structure Conditional

If statement , Switch statement, Conditional operator

s a emen

Tuesday, April 06, 2010 2Biju K Raveendran@BITS Pilani


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Control Structures

It is a combination of individual instructions

Only one entry point and one exit point

Selection control structure

A control structure that chooses among alternativeprogram s a emen s

Condition

n express on a s e er rue or a se What is TRUE and What is FALSE in C?

-



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Relational & Equality Operators

pera or ean ng

< Is less than

=

> Is greater than

>= Is greater than or equal to

== Is equal to

!= Is not equal to



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Relational & Equality Operators Most conditions will have one of the following forms

variable variable

variable constant

The variable / constant can be integer, float/double orcharacter



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Examples:5 = 0 FALSE

5.8 = 2.8

9 >= 0

=a


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Logical OperatorsOperator Meaning&& Logical AND

|| Logical OR

! Logical NOT

Used to test more than one condition

Example: a


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Logical Operators

in_range = (n > -10 && n < 10);

=


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Operand 1 Operand 2 Operand 1 && Operand 2

- -Non-Zero (TRUE) Zero (FALSE) 0 (FALSE)

Zero (FALSE) Non-Zero (TRUE) 0 (FALSE)

Zero (FALSE) Zero (FALSE) 0 (FALSE)

Operand 1 Operand 2 Operand 1 || Operand 2

Non-Zero (TRUE) Non-Zero (TRUE) 1 (TRUE)

Non-Zero (TRUE) Zero (FALSE) 1 (TRUE)

-

Zero (FALSE) Zero (FALSE) 0 (FALSE)

Non-Zero (TRUE) 0 (FALSE)

Zero (FALSE) 1 (TRUE)



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Assignment OperatorsSimple AssignmentOperators

Shorthand Operators

a = a+1 a+= 1

a = a-1 a-= 1

a =a*(b+1) a*=b+1

a = a/(b+1) a/=b+1

*

a = a%b a%=b



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operator expression Explanation Assigns

i 3 d 5 4 f 6 12Assume:intc = 3 ,d = 5 ,e = 4 ,f = 6 ,g = 12; += c += 7 c = c + 7 10 to c-= d -= 4 d = d - 4 1 to d*= e *= 5 e = e * 5 20 to e/= f /= 3 f = f / 3 2 to f= g = 9 g = g 9 3 g 9 g g 9 3



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Increment and Decrement Operators++ Adds one to the operand

-- Subtracts one from the operand

Both are unary operators

++ s equ va en o: = +

--i is equivalent to: i = i-1

is ++i and i++ are same??

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What is Postfix and Prefix?In postfix the expression is evaluated first using the

original value of the variable and then the variable is

incremented (or decremented) by one.

Ex.

m = n++;

In refix the variable is incremented or decrementedfirst and then the expression is evaluated using the

new value of the variable.

Ex.

m = n;



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Postfix and Prefix Examplesj =10;

i =j++;

What is the values of i and j?

=10;

i=++j;



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i = 10; j = 20;

= ;

What will be the value of i, j and k?

i = 10; j = 20;

k = i++ + ++j;

What will be the value of i and k?

k = ++i + ++j;

a w e e va ue o , an

Tuesday, April 06, 2010 Biju K Raveendran@BITS Pilani 16


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Operator Sample expression Explanation

++ ++a Increment a by 1, then use the new value of a in thea a . ++ a++ Use the current value of a in the expression in whicha resides, then increment a by 1.-- --b Decrement b by 1, then use the new value of b in theex ression in which b resides.

-- b-- Use the current value ofb in the expression in whichb resides, then decrement b by 1.



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Bitwise OperatorsOperator Meaning

& Bitwise AND

| Bitwise OR

^

> Shift right

Manipulation of data at bit level

May not be applied to float values

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Special Operators

The Size of Operator

occupies

Examples:

q=sizeof(float);

r=sizeof(long int);



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The comma operator

Used to link the related expressions together.

Evaluation starts from left to ri ht.

And the value of the right most expression is the valueof the combined expression.

Example:

, , ,

value contains 21

Use of comma o erator

for (i = 1, j = 15; i


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Operators Associativity Rank

(),[], ., -> L to R 1

Postfix ++ Postfix -- R to L 2Prefix ++, Prefix --, !, ~, sizeof, Unary +,

Unary -, Unary *, Unary &

R to L 3

*, /, % L to R 5Binary plus(+) and Binary minus (-) L to R 6

L to R 7

= L to R 8

==, != L to R 9

Binary & L to R 10

Binary ^ L to R 11

Binar L to R 12

&& L to R 13

|| L to R 14

?: R to L

=, *=, /=, %=, +=, -=, &=, ^=, |=, = R to L 16

, L to R 1721


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Short Circuit Evaluationa || b is true, if a is true, a && b is false, if a is false


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