[Haskell-cafe] ByteString in patterns

[Don Stewart]

manlio_perillo:
> Hi.
>
> Using normal String type I can define a pattern like:
>
> > let foo "baz" = 777
> > foo "baz"
> 777
>
>
> But if I want to use ByteString, what should I do?
> This seems impossible, since ByteString data constructor is not available.

-XOverloadedStrings

e.g.

    {-# LANGUAGE OverloadedStrings #-}

    import qualified Data.ByteString.Char8 as C

    isMatch :: C.ByteString -> Bool
    isMatch "match" = True
    isMatch _       = False

    main = print . map isMatch . C.lines =<< C.getContents