How about a language which allows you to define your own optimisations in source code? This reminds me of Nim's term rewriting macros which let you do precisel

How about a language which allows you to define your own optimisations in source code? This reminds me of Nim's term rewriting macros which let you do precisely that: http://nim-lang.org/docs/manual.html#term-rewriting-macros http://nim-lang.org/docs/manual.html#term-rewriting-macros