Jeremy Shaw wrote:

Hello,

GHC is happy to compile this code:

...

f x = (`head` x, ())

Also (+ x, ()) ((), + x) ((), + x, ()) are accepted by GHC This looks like a bug to me, because (+, ()) ((), x +) are rejected. Sections need to be in parens. If one allows sections as tuple components, then the latter should may be made legal, too. Cheers Christian

but Hugs does not like it, and Section 3.5 of the Haskell Report does not give any obvious indications that it is valid. Numerous people have suggested that some additional parens are required:

...

f x = ((`head` x), ())

Is this GHC behavior intentional? If not, is it perhaps a happy accident? Or is it ambigious in some way with out the additional parenthesis ?

I am curious because trhsx (the preprocessor for HSP/HSX) currently does not accept this construct. If it is a bug in GHC (that will eventually be fixed), then we can leave trhsx alone. If it is a feature, then a precise definition of the adjusted syntax would be helpful. (Or, if this construct is valid H98, an explaination of how to read the report correctly).

Thanks! j.