Why are loops not slow in Julia?

[mbauman]

Previously:

Why Are Languages Like Python and MATLAB So Much Slower than Julia?

The simplest answer is that, naively, higher level dynamic languages need to ask meta-questions about everything in order to figure out what to do. That is, given a function like: function mysum(array) r = zero(eltype(array)) for elt in array r += elt end return r end A traditional high-level language doesn’t know what elt will be — and it might not always be the same thing. So in every single iteration the language needs to ask: what type is elt? what type is r? wh…