Hello! I'm happy to announce the first release of HoleyMonoid, a datatype that helps you build monoids with holes in them. The holes are filled in later using normal function application. For example:

...

let holey = now "x = " . later show . now ", y = " . later show run holey 3 5 "x = 3, y = 5"

The library is available on Hackage: http://hackage.haskell.org/package/HoleyMonoid Thanks to David Menendez for the name and Sjoerd Visscher for help with rewriting and simplifying. :-) Martijn.