Am 26.10.2011 01:49, schrieb Tom Hawkins:
Can someone provide guidance on how handle operator precedence and
associativity with Polyparse?
Do you mean parsing something like "1 + 2 * 3" ? I don't think
there's any real difference in using Polyparse vs Parsec for this,
except for doing "p `orElse` q" rather than "try p<|> q".
Actually, I was looking for something equivalent to
Text.ParserCombinators.Parsec.Expr.buildExpressionParser. I suppose I
should learn how Parsec implements this under the hood.
I would do it as described under chainl1 in
http://hackage.haskell.org/packages/archive/parsec2/1.0.0/doc/html/Text-ParserCombinators-Parsec-Combinator.html
I believe Parsec.Expr cannot handle a prefix operator (i.e. unary minus)
properly, that has lower precedence than an infix operator (i.e. "^"
power). If it can parse "-x^2" as "-(x^2)" then if cannot parse "x^ -2"
as "x^(-2)".
Cheers Christian
-Tom
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