Maybe. But are you saying you can't pull a method invocation you know will return the same value every time outside of a loop without profiling? I doubt Rob Pik

Maybe. But are you saying you can't pull a method invocation you know will return the same value every time outside of a loop without profiling? I doubt Rob Pike believes that. Which leaves us with saying this is a rule of thumb, or what a speed hack is requires more commentary. I'm ok with a rule of thumb. I just want to point out that they leave a lot of room for disagreement and that the most important part may end up being how you apply the rule in particular cases.