CODEWITHSUNDEEP
cif-statementlogical-or
Joshua Ubani-Wokoma
Joshua Ubani-Wokoma

Reputation: 117

Solving a problem using logical operators in C programming language


#include <stdio.h>


void main()
{
 int a = 11, b = 5;
 if(a == 7 || 10){
     printf("True");
 }
 else
 printf("False");
}

This is my problem, i saw it in a question and was asked what the output would be. i put false but the answer was true, im trying to understand why because a is not equal to any of them and the condition for it to be true is that a be equal to at least one of them

Upvotes: 0

Views: 938

Answers (3)

Spiros
Spiros

Reputation: 99

It is a logical error. The way you type it you don't check whether a == 7 OR a == 10 (as you wish), rather you check only if a == 7 and second condition if (10) is always true.

The fix is pretty simple actually:

void main()
{
 int a = 11, b = 5;
 if(a == (7 || 10)){
     printf("True");
 }
 else
 printf("False");
}

Upvotes: 1

dbush
dbush

Reputation: 225227

This:

if (a == 7 || 10)

Does not test if a is equal to either 7 or 10.

The == operator will evaluate to 1 if both operands are equal, and 0 otherwise. The || operator will evaluate to 1 if at least one operand is non-zero, and 0 otherwise.

Also, the equality operator has higher precedence than the logical OR operator. So the above parses as:

if ((a == 7) || 10)

So the expression will be true if either a==7 evaluates to non-zero or 10 evaluates to non-zero. The latter is true so the condition is true.

Upvotes: 1

Vlad from Moscow
Vlad from Moscow

Reputation: 311108

The expression in the if statement

if(a == 7 || 10){

is equivalent to

if( ( a == 7 ) || ( 10 ) ){

As 10 is not equal to 0 then the second operand of the logical OR operator || always evaluates to the logical true. So the whole expression used in the if statement has a result of the logical true.

In fact as a is not equal to 7 (due to its initialization) then the above if statement is equivalent to

if( 10 ){

Upvotes: 3

Related Questions