Private default function arguments

[Clemens]

bearophile Wrote:

> But it also simplifies code, makes it a bit safer, avoiding some possible bugs both of the original problem and created by the alternative solutions.

What problems does the static inner function idiom create? It's clean, safe, performant, works with the current language and compiler, and has long precedent in other languages supporting nested functions. Lisp and Scheme do this all the time.