28 lines
474 B
Haskell
28 lines
474 B
Haskell
{-# Language TemplateHaskell, QuasiQuotes, FlexibleContexts #-}
|
|
|
|
import Text.Peggy
|
|
import AST
|
|
|
|
[peggy|
|
|
top :: AST = expr !.
|
|
|
|
expr :: AST
|
|
= expr "+" fact { Add $1 $2 }
|
|
/ expr "-" fact { Sub $1 $2 }
|
|
/ fact
|
|
|
|
fact :: AST
|
|
= fact "*" term { Mul $1 $2 }
|
|
/ fact "/" term { Div $1 $2 }
|
|
/ term
|
|
|
|
term :: AST
|
|
= "(" expr ")"
|
|
/ number
|
|
|
|
number ::: AST
|
|
= [1-9] [0-9]* { IntConst $ read ($1 : $2) }
|
|
|]
|
|
|
|
main :: IO ()
|
|
main = print . parseString top "<stdin>" =<< getContents |