CODEWITHSUNDEEP
clogical-operators
user3556306
user3556306

Reputation: 19

Evaluation && operator in C

While I was making a program in C, I came across a problem. && is not evaluating the second operand, if first is false. I know this is known as short circuit behavior. But I want second operand to be executed, see the code below to know why?

while(a-- && b--){
    //some statements
}

Please tell me different ways to accomplish my task. Thanks a lot!

Upvotes: 1

Views: 100

Answers (5)

haccks
haccks

Reputation: 105992

If you want the execution of second operand whether a is true or false then you can use comma operator. I think you need this: 

while((b--, a--) && b) {...}

Upvotes: 1

AnT stands with Russia
AnT stands with Russia

Reputation: 320361

Since you are using postfix decrement, the whole thing can be rewritten as simply

while (a && b)
{
  --a; --b;
  //some statements
}

--a; --b;

(Whether you really need that last line is for you to decide.)

But if you really want to keep everything stuffed into that while condition, there are different ways to achieve that as well. For example, you can replace && operator with & operator as long as you remember to "normalize" the operands with !!

while(!!(a--) & !!(b--)){
    //some statements
}

Upvotes: 2

Nishant
Nishant

Reputation: 2619

while(a && b){
     a--; b--;
     //some statements
}
// just after loop ends
a--; b--;

Upvotes: 1

bishop
bishop

Reputation: 39354

If you need decremented b after the loop, why not just make it first to guarantee evaluation?

while (b-- && a--)

Of course, this might not work if a and b are more complicated than your question indicates.

Upvotes: 0

Ian
Ian

Reputation: 861

If a and b are small enough such that a*b doesn't overflow:

while( (a--) * (b--) )
{...}

If they can be large:

while( ((a--) ? 0xf : 0) & ((b--) ? 0xf : 0) )
{...}

Upvotes: 2

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