[Haskell-cafe] Re: The Worker/Wrapper Transformation

[Isaac Dupree]

Achim Schneider wrote:
> Achim Schneider <barsoap at web.de> wrote:
> 
>> [...]
> 
> I'm trying to grok that
> 
> [] = id
> ++ = .
> 
> in the context of Hughes lists.

they are also known as "difference lists", and also used at type String 
in the Prelude as "ShowS", to help avoid quadratic behavior when making 
complicated Strings.  the [a]->[a] is not an ordinary function -- it's 
expected not to examine its argument, just to use it exactly once (is 
there a formal way to say that?)

~Isaac