> Yes, but it reports type errors for the variants
> f x = (\x -> x*x .)
> g x = (if x then 1 else 2 +)
> and it accepts
> h = (let op x y = y in 3 `op`)
> so I suspect it's misparsing these as
> f x = (\x -> (x*x .))
> g x = (if x then 1 else (2 +))
> h = (let op x y = y in (3 `op`))
But I would claim that nhc98 is parsing these correctly, at least
according to section 3 of the Report.
" The grammar is ambiguous regarding the extent of lambda
abstractions, let expressions, and conditionals. The ambiguity is
resolved by the meta-rule that each of these constructs extends
as far to the right as possible. As a consequence, each of these
constructs has two precedences, one to its left, which is the
precedence used in the grammar; and one to its right, which is
obtained via the meta-rule. "
In the table of precedence in the original Report (now deleted in
the revised Report), it makes it clear that a rightward-extending
let, if, or lambda has a lower precedence than an infix operator,
so for instance the parse
h = (let op x y = y in (3 `op`))
is correct and
h = ((let op x y = y in 3) `op`)
is not.
Regards,
Malcolm
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