leledumbo wrote:
consider this partial program: if n>5 then putStrLn "big" else putStrLn "small"
this works fine in hugs, but in ghc I must change it to: if n>5 then putStrLn "big" else putStrLn "small"
Actually both of those are valid expressions. And they both work in hugs and ghc. The question I imagine you're asking involves layout mode: do if n>5 then putStrLn "big" else putStrLn "small" this is shorthand for do { if n > 5 then putStrLn "big" ; else putStrLn "small" } which is a syntax error. A statement in a do block cannot begin with the keyword "else". If you indent the else a bit further than it counts and a continuation of the enclosing expression (beginning with if) so it desugars to do { if n > 5 then putStrLn "big" else putStrLn "small" } which is fine. Haskell' is apparently going to include a hack to permit this case. I think that's a poor decision, because including a hack to the layout rule makes it harder to understand and explain the layout rule. Jules