CODEWITHSUNDEEP
if-statementlogic
Paul Bajan
Paul Bajan

Reputation: 21

If expression with question mark. What does it translate to with a normal if else instruction

I have this expression which I know is an if statement...but what does it translate to? flag = flag?0:1; Is it : if (flag==flag) flag=0 else flag =1 if this is the case then flag will become 1 once when timer reaches 12500 but it will never become 0 again. right?

int flag = 0; 
while(1)
  {
     if (timer == 12500)
       {
          flag = flag?0:1;
          timer=0;
       }

     if(flag == 1)

      p4_0=0; //turn on LED0

    else

      p4_0=1; //turn off LED0

    timer++;
   }

Thanks!

Upvotes: 0

Views: 1035

Answers (3)

Amit
Amit

Reputation: 195

(flag = flag?0:1) means that if(flag) then flag=0 otherwise flag=1.To be more precise,if the value of flag is 0 then flag will become 1 otherwise for all non-zero value flag will become 0. Its use in your code is that as soon as the timer reaches 12500 the flag will become 1 and the LED will be turned on and it will remain ON henceforth.

Upvotes: 1

ServerSocketAccept
ServerSocketAccept

Reputation: 74

flag = flag?0:1; Means if flag is 0 then it is zero, if flag >0, then flag becomes 1.

Upvotes: 0

Mike Corcoran
Mike Corcoran

Reputation: 14565

that is a ternary expression

var = var ? expression1 : expression2

means if var is truthy, assign expression1 to var, else assign expression2 to var. basically this.

if (var)
    var = expression1
else
    var = expression2

so in the code you have above, when the timer == 12500, the flag will be reset and turn off LED0.

Upvotes: 1

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