On 03/03/15 05:00 AM, Cody Goodman wrote:

-- trying to parse the text below using Parsec:

-- ACT I.

-- SCENE I. An open place. -- [An open place. Thunder and lightning. Enter three Witches.]

-- FIRST WITCH. -- When shall we three meet again -- In thunder, lightning, or in rain?

-- Here's the code I have

import Text.Parsec import Control.Applicative import Data.Traversable (sequenceA)

section s = sequenceA [string s, string " ", many1 letter] `endBy` char '.'

act = section "ACT" scene = section "SCENE"

main = do parseTest act "ACT I.\n" parseTest scene "SCENE I."

-- this returns: -- λ> main -- [["ACT"," ","I"]] -- [["SCENE"," ","I"]]

-- Am I using Parsec correctly so far?

The act, scene, and section functions are just fine. The main function is probably not, unless you really intend your act and scene to be two different inputs. The parseTest function should generally be used only once, and it should be applied to the entire parser. So what you want is more like

parser = do act string "\n" scene

main = parseTest parser "ACT I.\nSCENE I."

Note that the result of the act function is being discarded in this example. You'll probably want to preserve it somehow, but unless you just want to print it you'll need to decide what kind of result you want to construct. It's generally a good idea to do that before setting out to write the parser itself.