Re: [Haskell-cafe] Parsec Expected Type

On 3/28/08, Paul Keir wrote:

What I'd like is to parse either the string "parameter", or the string ":". I'm using 'reserved' and 'symbol' because they seem to correspond well to the concepts in the language I'm parsing. I could try,

tester3 = reserved "parameter" <|> do { symbol ":"; return () }

Actually this is exactly on the right track. But I agree, it looks a bit contrived. Maybe this looks better to you?

tester3 = reserved "parameter" <|> (symbol ":" >> return ())

Or you could factor this behavior out into a new combinator:

or_ :: Parser a -> Parser b -> Parser () or_ x y = (x >> return ()) <|> (y >> return ())

tester3 = reserved "parameter" `or_` symbol ":"

-- ryan