On 25-Aug-1999, Keith Wansbrough <[EMAIL PROTECTED]> wrote:
> According to the Haskell 98 report, patterns have the following grammar:
>
> apat ::= var [ @ apat ]
> | ~ apat
> | ...etc...
>
> Thus the following program should be legal (IMHO):
>
> main = let foo@~(x,y) = (1,2)
> in print foo
>
> Instead, both Hugs and GHC report
>
> ERROR "TestAsPat.hs" (line 1): Undefined variable "foo"
>
> What have I missed?
What's the lexical syntax? Is `@~' one token, or two?
I haven't checked the Haskell report, but I suspect that the
problem with your example is that `@~' is being parsed as a single
token, so the grammar rules containing `@' and `~' don't apply since
there is no `@' or `~' token in your example, only a `@~' token.
Try replacing `@~' with `@ ~' and see if that helps.
--
Fergus Henderson <[EMAIL PROTECTED]> | "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh> | of excellence is a lethal habit"
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