[Haskell-cafe] Happy Parsers and constraints
Alan & Kim Zimmerman
alan.zimm at gmail.com
Thu May 18 20:32:29 UTC 2017
Hi all
If I have a happy parser for an AST that is polymorphic, is there any way
to put constraints on the individual rules?
e.g. if I have
data Foo a = Foo String a
and a rule something like
foo :: { (Show a) => Foo a }
foo : otherrule { Foo (show $1) $1 }
Because of the way the tables are constructed in happy, the Show constraint
is not attached to the point where the rule RHS is applied.
Is this simply impossible?
Alan
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