[Haskell-cafe] what does ' mean?

[Jonathan Cast]

Logesh Pillay <logesh at iafrica.com> wrote:
> Dear list
> 
> A v. newbie question.
> 
> I found the following code on the web
> 
> /-- Andrew Bromage
> /
> /-- If you're doing permutations, then I suppose you want this too:
> //-- (subLists might be a more suggestive name)
> /combinations *:: [a] -> [[a]]
> *combinations [] = [[]]
> combinations (x:xs)
>     = combinations xs ++ [ x:xs' | xs' <- combinations xs ]
> 
> What does ' (apostrophe) mean?  I see no reference to it in Simon 
> Thompson's book.

In  Haskell, '  following  a letter  or  number in  a  variable name  is
considered a part of the variable name.  So, xs' is just a variable name
distinct from xs.

Jon Cast