Result monad

[Malcolm Matalka]

I've been playing with writing code that can fail in a lot of ways and
using Result.Monad_infix to make it more readable.  I've found that this
only really works well if all of my functions that return a Result.t
have polymorphic variants on the Error side.  Is this the suggested best
practice as well?  I'm considering just mandating all my code that can
return a Result.t does this.

Thanks,
/Malcolm