An elegant way to clean data is by defining a lexer to split up a string into tokens. In this recipe, we will parse an e-mail address using the attoparsec library. This will naturally allow us to ignore the surrounding whitespace.
Create a new file, which we will call Main.hs, and perform the following steps:
Use the GHC
OverloadedStringslanguage extension to more legibly use theTextdata type throughout the code. Also, import the other relevant libraries:{-# LANGUAGE OverloadedStrings #-} import Data.Attoparsec.Text import Data.Char (isSpace, isAlphaNum)Declare a data type for an e-mail address:
data E-mail = E-mail { user :: String , host :: String } deriving ShowDefine how to parse an e-mail address. This function can be as simple or as complicated as required:
e-mail :: Parser E-mail e-mail = do skipSpace user <- many' $ satisfy isAlphaNum...