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improved error reporting in .ebnf format parser

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aarne
2006-11-24 17:09:40 +00:00
parent 35eaaa0da6
commit 13531a66a3
1 changed files with 5 additions and 2 deletions
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7
src/GF/Data/Parsers.hs
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@@ -33,6 +33,7 @@ module GF.Data.Parsers (-- * Main types and functions
import GF.Data.Operations import GF.Data.Operations
import Data.Char import Data.Char
import Data.List
infixr 2 |||, +|| infixr 2 |||, +||
@@ -51,10 +52,12 @@ type Parser a b = [a] -> [(b,[a])]
parseResults :: Parser a b -> [a] -> [b] parseResults :: Parser a b -> [a] -> [b]
parseResults p s = [x | (x,r) <- p s, null r] parseResults p s = [x | (x,r) <- p s, null r]
parseResultErr :: Parser a b -> [a] -> Err b parseResultErr :: Show a => Parser a b -> [a] -> Err b
parseResultErr p s = case parseResults p s of parseResultErr p s = case parseResults p s of
[x] -> return x [x] -> return x
[] -> Bad "no parse" [] -> case
maximumBy (\x y -> compare (length y) (length x)) (s:[r | (_,r) <- p s]) of
r -> Bad $ "\nno parse; reached" ++++ take 300 (show r)
_ -> Bad "ambiguous" _ -> Bad "ambiguous"
(...) :: Parser a b -> Parser a c -> Parser a (b,c) (...) :: Parser a b -> Parser a c -> Parser a (b,c)