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

After reading [Hidden Features and Dark Corners of C++/STL][1] 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?

[1]:

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The usage of `-->` has historical relevance. Decrementing was (and still is in some cases), faster than incrementing on the x86 architecture. Using `-->` suggests that `x` is going to `0`, and appeals to those with mathematical backgrounds.

There is a space missing between `--` and `>`. `x` is post decremented, that is, decremented after checking the condition `x>0 ?`.

`--` is the **decrement** operator and `>` is the **greater-than** operator.

The two operators are applied as a single one like `-->`.

Utterly geek, but I will be using this:

#define as ;while

int main(int argc, char* argv[])
{
int n = atoi(argv[1]);
do printf("n is %d\n", n) as ( n --> 0);
return 0;
}

Anyway, we have a "goes to" operator now. `"-->"` is easy to be remembered as a direction, and "while x goes to zero" is meaning-straight.

Furthermore, it is a little more efficient than `"for (x = 10; x > 0; x --)"` on some platforms.