unwords with optional record separator is hard to write?
I was chatting with Cale on #haskell and said that unwords should be configurable: it should take an optional argument specifying what to separate the elements of the list with.
He said that would be hard.
It is a common thing in Perl and Lisp for a function to assume defaults if you don't specify things.
I guess the best thing to do in Haskell is to always expect the separator to be specified and have the function curryable on the input list to be unworded:
unwords :: String -> [a] -> String
unwords sep lis = blah blah