Dear Gunther, I am providing my solution, on which one can of course specialise in making sure that a valid date is parsed, which would be a bit more cumbersome; how should e.g. error correction be done. I prefer to test afterwards in such situations. Best, Doaitse module Guenther where import Text.ParserCombinators.UU.Parsing import Text.ParserCombinators.UU.BasicInstances import Text.ParserCombinators.UU.Examples hiding (main) import Control.Applicative hiding ((<*), (*>), (<$)) {- The first decision we have to make is what kind of input we are providing. The simplest case is just to assume simple characters, hence for our input type we will use the standard provided stream of Characters: Str Char, so we use the type of our parsers to be the type used in the Examples module; since we do not know whether we wil be using the parsers in a monadic mode too we stay on the safe side ans use the type P_m -} type GP a = P_m (Str Char) a -- GP stands for GuenterParser {- Once we know that our input contains characters, but that in our output we what to have integer values, we start out by building a parser for a single integer , for which we use the function pNatural form the examples-} pDate = (,,) <$> pNatural <* pDot <*> pNatural <* pDot <*> (pNatural ::GP Int) pDot = pSym '.' {- main = do print (test pDate "3.4.1900") print (test pDate "3 4 1900") print (test pDate "..1900")-} -- end of Module Guenther By playing with insertion and deletion costs (e.g. by building a more picky pNatural) one can control the error recovery. Another option to get better error recovery would be to define a specialised instance of Provides which removes spaces. You might even temporarily pSwitch to the use of this state
Period.
I do not even manage to write a parser for even a mere digit or a simple character. I have read the tutorial from a to a to z and from z to a and there were a few words I recognized.
I mean I'd like to be able to turn "12.05.2009" into something like (12, 5, 2009) and got no clue what the code would have to look like. I do know almost every variation what the code must not look like :).
I am guessing here that when one does define a parsing function, since all the parser combinators aren't function but methods, one *must* also provide a type signature so that the compiler knows the actual *instance* method?
Günther