What is the "-->" operator in C++?


After reading Hidden Features and Dark Corners of C++/STL on comp.lang.c++.moderated, I was completely surprised that the following snippet compiled and worked in both Visual Studio 2008 and G++ 4.4.

Here's the code:

#include <stdio.h>
int main()
    int x = 10;
    while (x --> 0) // x goes to 0
        printf("%d ", x);

I'd assume this is C, since it works in GCC as well. Where is this defined in the standard, and where has it come from?

2/13/2017 8:32:20 AM

Accepted Answer

--> is not an operator. It is in fact two separate operators, -- and >.

The conditional's code decrements x, while returning x's original (not decremented) value, and then compares the original value with 0 using the > operator.

To better understand, the statement could be written as follows:

while( (x--) > 0 )
12/23/2018 3:46:05 PM

Or for something completely different... x slides to 0

while (x --\
               > 0)
     printf("%d ", x);

Not so mathematical, but... every picture paints a thousand words...

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