Ian Lynagh wrote:
On Thu, Mar 09, 2006 at 04:53:52PM -0000, Simon Marlow wrote:
the problem is that 'let' does not always have a
matching 'in', e.g. when it is used in 'do', pattern guards or list
comprehensions. So you can't consistently treat let/in as brackets.
Right, I mentioned that in my earlier mail. However, I think this can be
handled by rules like
L (<n>:ts) ((Let:bs,m):bsms) = L ts ((bs,m):bsms) if m = n
Here's a tricky case:
... | let x, y :: T
x = 3
y = 4,
...
The first , shouldn't close the let statement, but the second should. How do
you distinguish between them? If you never allow , to close a let statement,
then you can no longer write
... | let x = 3, ...
Of course, the commas in type signatures and fixity declarations are
redundant anyway. If they were dropped from the grammar, this problem would
go away.
Incidentally, in my head the "," in "(case x of p -> e, 42)" acts as a
right and left bracketing lexeme, so this expression would still be
accepted.
Here's another tricky case:
(case p of q | r,s -> t, ...)
I'm not sure what to do about this one.
-- Ben
_______________________________________________
Haskell-prime mailing list
[email protected]
http://haskell.org/mailman/listinfo/haskell-prime
