As if coffeescript originated the features... We don't have iteration with index variable because it's seen as extraneous and unnecessary. If you aren't using i

As if coffeescript originated the features... We don't have iteration with index variable because it's seen as extraneous and unnecessary. If you aren't using iterators, you're paying for unnecessary bounds checks (LLVM often can't optimize them out). The explicit let mostly comes from the ML heritage and want for nice pattern matching.