New subject: Is there any way to use somethig like global backtrack with parsec

30 May 2016

      If don't have to use Parsec, you can use a parser library like ReadP / 
ReadS.

For example:

import Text.ParserCombinators.ReadP

abc =  (choice [ string "a", string "ab" ] ) >> char 'c' >> eof

run p s = case (readP_to_S p) s of
            []         -> Left "no parse"
            ((a,_):_)  -> Right a

test1 = run abc "ac"
test2 = run abc "abc"
test3 = run abc "ab"  -- should fail

On Monday, May 30, 2016 at 1:15:25 PM UTC-5, Petr Sokolov wrote:
...
For example this parser doesn't parse "abc"
test :: Parser String
test = ((try $ string "a") <|> (string "ab")) *> (string "c")
I can rewrite it so it would parse "abc", but is there any general 
approach to force parser to return and try other branches?
(try a <|> b) *> c
Something like
(tryOtherBranchesIfFail (try a <|> b)) *> c
So if it cannot parse "abc" with (try a *> c) it could return and try (b 
*> c)
Or it isn't possible?

Re: [Haskell-cafe] Is there any way to use somethig like global backtrack with parsec

Erik Rantapaa

S. Doaitse Swierstra

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