This isn't quite what you're asking for, but by using the applicative interface to parsers, you need do little more than spell out what your AST looks like:
import Control.Applicative
import Control.Applicative.Infix
data Equation = String :=: Expression
data Expression = EApp fun arg | EInt Int | EId String
parseEquation :: Parser Equation
parseEquation = parseIdentifier <^(:=:)^> parseExpression
parseExpression :: Parser Expression
parseExpression =
(EApp <$> parseExpression <*> parseExpression)
<|> (EInt <$> parseInt)
<|> (EId <$> parseIdentifier)
parseIdentifier :: Parser String
parseIdentifier = parseLowercaseChar <^(:)^> parseString
etc
Bob
On Sun, Dec 27, 2009 at 10:18 AM, CK Kashyap
<ck_kashyap@yahoo.com> wrote:
Hi All,
I recently came across the paper titled "Monadic Parser Combinators" - After going through it a few times, I think I am beginning to understand monads.
However, the parser developed in the paper does not generate an AST - I feel, I'd grasp the whole thing a lot better if I could go over a sample that generates an AST from a simple expression (or even a standard language such as C or Java) ... Can someone please point me to a sample that generates AST - preferably with the simple parser combinator given in the paper.
Regards,
Kashyap