6502 assembly language as a haskell monad (for programming NES games) http://www.wall.org/~lewis/2013/10/03/inverting.html Looks 99% like regular 6502 ASM, but can be refactored into haskell functions. Awesome!

Quite simple implementation details here: http://wall.org/~lewis/2013/10/15/asm-monad.html

By my count, it took 25 lines of code to write this beyond-full-featured assembler.