Personally I love Haskell, but I did a bunch of mathematical logic at university so that might explain it :) For practical work though I think hybrid FP/OO lan

Personally I love Haskell, but I did a bunch of mathematical logic at university so that might explain it :) For practical work though I think hybrid FP/OO languages like Ruby and Scala (maybe Python and LISP too) are usually a better choice. Pure functional programming requires too much of an appreciation of higher structural aspects of mathematics, logic and theoretical computer science, to be viable for use with mixed-background teams on bigger projects. I'm also not convinced Monads are the final word as a scalable structure for software engineering with FP. I think (hope?) research will yield something better. But in environments where a lot of smart math/comp-sci oriented people work on a codebase, I think something pure functional can be a good choice. eg stuff like darcs (which is very algebraic), compilers, comp sci research, people at algorithmic trading firms, projects that want powerful code verification capabilities.