Programmer Humor

I never looked into this, so I have some questions.

Isn't the overhead of a new function every time going to slow it down? Like I know that LLVM has special instructions for Haskell-functions to reduce overhead, but there is still more overhead than with a branch, right? And if you don't use Haskell, the overhead is pretty extensive, pushing all registers on the stack, calling new function, push buffer-overflow protection and eventual return and pop everything again. Plus all the other stuff (kinda language dependent).

I don't understand what advantage is here, except for stuff where recursive makes sense due to being more dynamic.