module OneLineAttrs(parseOneLineAttrs) where
import Monad
import Maybe
import Char
--import Attrs
A parser for attribute descriptions like these two:
name=hyp, type=string, label="Depends on", optional
name=conc, type=string/assertion, label="Conclusion", required
--type Attr = (String, String) -- tag, value --type Attrs = [Attr] --parseOneLineAttrs :: String -> Maybe Attrs
parseOneLineAttrs = complete parseOneLineAttrs' parseOneLineAttrs' = manySep comma parseOneLineAttr comma s = [((),r)|(",",r)<-lex s] parseOneLineAttr s = [((name,value),r)|(name,r1)<-lex s, (value,r)<-parseValue r1] parseValue s = [(value,r)|("=" ,r1)<-lex s, (value,r)<-lexval r1] `orelse` [("",s)] lexval s = case s' of [] -> [] '"':_ -> reads s' -- string literal _ -> [span isAttr s'] where s'=dropWhile isSpace s isAttr c = c/=',' && isPrint c -- Parsing combinators for the ReadS type: xs `orelse` ys = take 1 (xs++ys) many p s = some p s `orelse` empty s some p s = [(x:xs,r)|(x,r1)<-p s,(xs,r)<-many p r1] empty s = [([],s)] prefix p1 p2 s = [xr|(_,r1)<-p1 s,xr<-p2 r1] someSep sep p s = [(x:xs,r)|(x,r1)<-p s, (xs,r)<-many (prefix sep p) r1] manySep sep p s = someSep sep p s `orelse` [([],s)] complete p s = listToMaybe [x|(x,r)<-p s,("","")<-lex r]