[OT] Money for nothing, and your bit flips for free?

[Nicholas Leippe]

On Wednesday 07 February 2007 16:13, Steve wrote:
> Turns out I had to create an assignment to get it function as I wanted.
>
> s[y] = ~s[y];

Yes, that would seem more correct.

[snip]

> inline void flip(std::string& s){
> 	int y = 0;
> 	while(y++ < s.length()){
> 		s[y] = ~s[y];
> 	}
> }

Try this optimization:

inline void flip(std::string& s) {
	int len = s.length(); // compute the string length only once
	for (int y = 0; y < len; y++) {
		s[y] = ~s[y];
	}
}


Depending on how std::string.length() is implemented, the compiler may already 
have been able to do this optimization for you.  You can test by comparing 
both sets of code with optimizations turned off.