CODEWITHSUNDEEP
haskelltext
Rumca
Rumca

Reputation: 1829

In Haskell, what is the reason for needing to convert from Data.Text.Internal?

Text.Regex.TDFA.Text is the only one that provides instances for RegexLike Regex Text using internal Text types.

Can instances of classes with Data.Text.Lazy be derived from instances of Data.Text.Internal? How can I improve this code?

import qualified Data.Text.Lazy as T
import Text.Regex.TDFA
import Text.Regex.Base.Context()
import Text.Regex.Base.RegexLike()
import Text.Regex.TDFA.Text
import Data.Function (on)

(<?>) :: T.Text -> T.Text -> Bool
(<?>) = on (=~) T.toStrict

Upvotes: 2

Views: 135

Answers (1)

Michael
Michael

Reputation: 2909

I might be missing something, but it seems you have missed the module containing lazy Text instances for the regex-tdfa classes . If that's what's happening, then you need only change

 import Text.Regex.TDFA.Text

to 

 import Text.Regex.TDFA.Text.Lazy

Note that what is called Text in the module Data.Text.Internal is the same as what is called Text in Data.Text -- i.e., it's "strict" Text. The lazy text type is defined in a different internal module (basically as a specialized list of strict texts.) So it's not as though these are two ways of viewing the same thing, if that's what you were thinking.

Upvotes: 4

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