sebf at informatik.uni-kiel.de
Wed Feb 10 04:40:34 EST 2010
On Feb 9, 2010, at 10:43 PM, S. Doaitse Swierstra wrote:
> -- but if we now unfold the definition of one we get a parser error
> in GHC
> increment' = ( let x=1 in x + )
> The GHC and Hugs parsers are trying so hard to adhere to the meta
> rule that bodies of let-expressions
> extend as far as possible when needed in order to avoid ambiguity,
> that they even apply that rule when there is no ambiguity;
> here we have only a single possible parse, i.e. interpreting the
> offending expression as ((let x = 1 in ) +).
Despite the fact that there is a typo (second x is missing), I can
think of two possible parses. Actually, my mental parser produced the
((let x=1 in x)+)
let x=1 in (x+)
The Haskell report may exclude my mental parse because operator
sections need to be parenthesised.
Or are you arguing that in your example different possible parses have
the same semantics for an arguably obvious reason and that this fact
Underestimating the novelty of the future is a time-honored tradition.
More information about the Haskell-prime