Update statement in empty for loop

Question

A similar question has been answered here[https://stackoverflow.com/a/13421435/3276830 ]. The author says

The following code

 for (i=0;i<5;i++);
 {
     printf("hello\n");
 }

is interpreted as follows:

Repeat five times for (i=0;i<5;i++)

... do nothing (semicolon)

Open a new scope for local variables {

... Print "hello"

Close the scope }

However, for the following for loop

int i = 0;
for(;i++;cout<<i<<" ");
cout<<i<<" ";

The output I get is just 1, but I expected it to be 123456.....

Edit, I know the difference between prefix and postfix operation. But yeah I did miss that it was 0 the first time loop ran.

Your continue condition is `i++` which quickly evaluates to 0 which is falsey — Nick is tired, Oct 05 '17 at 14:04
Possible duplicate of [What is the difference between prefix and postfix operators?](https://stackoverflow.com/questions/7031326/what-is-the-difference-between-prefix-and-postfix-operators) — Christopher Pisz, Oct 05 '17 at 14:08
@ChristopherPisz I know the difference between prefix and postfix operation. But yeah I did miss that it was 0 the first time loop ran. — Varun Garg, Oct 05 '17 at 14:12

score 3 · Accepted Answer · answered Oct 05 '17 at 14:05

3

int i = 0;
for(;i++;cout<<i<<" ");

This loop can never execute because i is 0, so i++ evaluates to 0 (the value before incrementing it) which is false. Try ++i instead.

answered Oct 05 '17 at 14:05

score 1 · Answer 2 · answered Oct 05 '17 at 16:10

1

the

for(;;i++, cout<<i<<" ");

looks more aesthetically :) correct and will work no matter prefix or postfix

answered Oct 05 '17 at 16:10

StahlRat

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Update statement in empty for loop

2 Answers2