the xs' is just a variable as xs,xs_, _xs. perhaps imply some relations with the counterpart without apostrophe suffix,but this is not mandatory.
----- Original Message -----
From: "Logesh Pillay"
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.
Thanks
Logesh
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