What is the '-->' operator in C/C++?

ghz 1years ago ⋅ 2921 views

Question

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. I would assume this is also valid C since it works in GCC as well.

Here's the code:

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

Output:

9 8 7 6 5 4 3 2 1 0

Where is this defined in the standard, and where has it come from?

Answer

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

The code in the condition 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 )
#c