Gabriel439/Haskell-Errors-Library — pull request #26 by k0001 (2014-03-14 20:30:46+00:00)
Title: Added isJustT, isNothingT, isLeftT, isRightT

I find these helpful, particularly `isJustT` when using `MaybeT` to `guard` against bad scenarios just to return `()` at the end if everything was OK.