Weird while loop

[Them]

okay maybe not so weird...

while (i--)
{
//some code goes here...
}

I have never seen a while loop that takes i-- as a condition. What does this mean in terms of the while loop?

Thanks so much.

[Disch]

Ugh... what an ugly loop conditon.


The condition of a while loop evaluates to either true (if nonzero) or false (if zero). So while(6) is the same as while(true)... and while(i) is the same as while(i != 0).

That said... i-- evaluates to the OLD value of i (prior to decrementing). Therefore:

int j = i--;

// is the same as:

int j = i;
i--;

So the loop basically decrements i before each iteration, and the loop stops when i drops below zero (because the old value of i would've been zero).

It's confusing, yes. This is an ugly loop.

It'd work out like this:

int i = 5;
while(i--)
{
  cout << i;  // 43210
}
cout << i; // -1 

[Them]

The way you described it is actually not that confusing.

Thank you.

[god]

well it wont work i think...
cause i know about loops is this...


while ( condition ){
//here lies the operations such as 'x = y' and etc. and as well as the
//updater like 'x += 1' , x++, x-- and so on.
}

for ( initiator; condition; updater ){
//operations
}
//initiator is like the initializer it set value of the updater and condition or what so ever needed in //the for loop

do {
//operations
//updater
} while ( conditions);

jah get it?

[jsmith]

Well waddaya know... god isn't omniscient after all.

condition is any expression that can be converted to bool. C, and therefore C++, allows
implicit conversion from int to bool, and guarantees that the integer value zero equates
to false, and all other integer values equate to true.

[god]

wow... god was amazed!!!!