A short post about using const in C++. <\/p>\n
Consider the following 3 for-loops in C\/C++:<\/p>\n
\/* Loop 1: *\/<\/p>\n
for(int i = 0; i < getSomeValue(); ++i) { ...lots of stuff in here... }<\/p>\n
\/* Loop 2: *\/<\/p>\n
int n = getSomeValue();<\/p>\n
for(int i = 0; i < n; ++i) { ...lots of stuff in here... }<\/p>\n
\/* Loop 3: *\/<\/p>\n
const int n = getSomeValue();<\/p>\n
for(int i = 0; i < n; ++i) { ...lots of stuff in here... }<\/p>\n<\/div>\n
Best Practice: If the value of 'n' is not supposed to change throughout the lifetime of the loop, then I think everyone can agree that using const in Loop 3 is a best practice. This helps ensure that some other coder doesn't muck about with the loop's end condition inside the loop (since it will be flagged with a compiler error).<\/p>\n
Optimization: It makes sense that, in general, Loop 2 would execute faster than Loop 1. But I was curious if a compiler could optimize Loop 3 to make it run faster than Loop 2? It's been awhile since I looked at any assembly output, and my compiler theory has always been rather weak, so I thought I'd throw the question out there in case anyone has a clue...<\/p>\n