Re: [Haskell-cafe] what does ' mean?

Logesh Pillay wrote:

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.

' nothing. xs' does the same as xs_, or _xs, or xs2, but it's readable.