Erik Meijer, John Launchbury and I discussed the syntax of implicit
parameters at WG2.8 last week.
We emerged with agreement on the following: instead of 'with' use
let dynamic
?x = 3
?y = ?y+?x
in
...
* 'dynamic' is a special-id, only significant immediately following
a let.
* The bindings are non-recursive, and nested top to bottom
Reasons:
- All other Haskell constructs are prefix form, and extend as far
to the right as possible: let, case, lambda. Using the same
convention
eliminates the question of what
let x = 4 in E with ?y = 4
might mean
The exception to prefix form is 'where' but it scopes over groups
of right-hand sides, not expressions
- We wanted a clear clue that this is not a standard-Haskell recursive
let
- We didn't want to take an extra keyword.
I (very much) hope this is acceptable to everyone. It's not worth
a major use of brain cells, but it would be great to make GHC and
Hugs agree.
Simon
PS: I recall that Alastair volunteered to make the change to Hugs.
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