2010/1/20 Heinrich Apfelmus
Static typing is a great help, it is not uncommon for Haskell code to be correct on the first try once you convinced GHC that it's type correct. There is much less need for TDD than in other languages.
Ah, maybe the type checker is given all credit here, when perhaps it should be shared? With functional programming languages you are largely programming with expressions - Scheme has the (begin ... ...) form for sequencing and ML has sequence control structure (;), but there is simply less control flow in typical functional programs than imperative ones (there is also less use of assignment but that's hardly news of course). Figuratively speaking, functional programs have 'fewer movable parts' to go wrong (vis-a-vis incrementing variable for loop indexes etc. whereas map, fold, unfold, ... can be written once and used anywhere), hence static-typing + control-flow reduction (+ limited use of side effects) hopefully leads to first-time correctness. Best wishes Stephen