This last piece of conversation was *so* reminiscent of a paper[1] I once
read, I was almost convinced it was late by 11 days...until I checked :)
Cheers,
Dinko
[1] http://www.research.att.com/~bs/whitespace98.pdf
On 4/12/07, Simon Marlow <[EMAIL PROTECTED]> wrote:
Isaac Dupree wrote:
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> Isaac Dupree wrote:
>> Simon Marlow wrote:
>>>> I definitely think that -1# should be parsed as a single lexeme.
>>>> Presumably it was easier at the time to do it the way it is, I don't
>>>> remember exactly.
>>>>
>>>> I'd support a warning for use of prefix negation, or alternatively
you
>>>> could implement the Haskell' proposal to remove prefix negation
>>>> completely - treat the unary minus as part of a numeric literal in
the
>>>> lexer only. This would have to be optional for now, so that we can
>>>> continue to support Haskell 98 of course.
>>>>
>>>> Cheers,
>>>> Simon
>> Yes, I've been thinking about how to implement both - details will come
>> later when I have more time. I think I have a reasonably working idea
>> of how to divide up the cases for warnings for ambiguous-looking use of
>> both infix and prefix minus, as well as actual syntax changes...
>
> not considering warnings, just syntax: 123abc is two valid Haskell
> tokens. for example:
> \begin{code}
> main = (\n c -> print (n,c)) 123Abc
> data Abc = Abc deriving Show
> \end{code}
> prints (123,Abc).
> So does this suggest that under a negation-is-part-of-numeric-token
> regime, 123-456 should be two tokens (a positive number then a negative
> number, here), as is signum-456 ...
Yes, absolutely.
> Presently, GHC doesn't even warn about the first thing (123abc) ^_^
and remember that while '123e 4' is 3 tokens, '123e4' is only 1.
Cheers,
Simon
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Cheers,
Dinko
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