How can I use parsec to parse all matched input in a string and discard the rest?
Example: I have a simple number parser, and I can find all the numbers if I know what separates them:
num :: Parser Int
num = read <$> many digit
parse (num `sepBy` space) "" "111 4 22"
But what if I don't know what is between the numbers?
"I will live to be 111 years <b>old</b> if I work out 4 days a week starting at 22."
many anyChar doesn't work as a separator, because it consumes everything.
So how can I get things that match an arbitrary parser surrounded by things I want to ignore?
EDIT: Note that in the real problem, my parser is more complicated:
optionTag :: Parser Fragment
optionTag = do
string "<option"
manyTill anyChar (string "value=")
n <- many1 digit
manyTill anyChar (char '>')
chapterPrefix
text <- many1 (noneOf "<>")
return $ Option (read n) text
where
chapterPrefix = many digit >> char '.' >> many space
For an arbitrary parser myParser, it's quite easy:
solution = many (let one = myParser <|> (anyChar >> one) in one)
It might be clearer to write it this way:
solution = many loop
where
loop = myParser <|> (anyChar >> loop)
Essentially, this defines a recursive parser (called loop) that will continue searching for the first thing that can be parsed by myParser. many will simply search exhaustively until failure, ie: EOF.