CODEWITHSUNDEEP
haskell
Ulrar
Ulrar

Reputation: 983

Capture group names with regex

I'm trying to use the regex package (with TDFA) and the only reference I can find for named captures group is a quasi quoter (cp) and no explanation. Basically I have regexs in a config files, compiled at runtime with compileRegex, applied to lines and I'm looking to extract a couple of specific captures group out of that, with names I do know at compile time.

So I'm looking for a function that would take the Matches a, a string (the capture group name) and would return I guess a Maybe a, depending on whether that capture group did match or not ? Or even just a way to extract the capture group names from the Match a, that would be enough.

The doc mentions the quasi quoter cp, but no explanation as to how it's supposed to be used, and I'm not even sure I could use if if I knew because I compile my regex at runtime.

Would anyone have examples with named capture groups ? Thanks

Upvotes: 1

Views: 159

Answers (1)

user11228628
user11228628

Reputation: 1526

You'll find the API you need in the Text.RE.Replace docs; I think one of the functions with names that start with capture will be what you're looking for. Here's an example:

module Main where

import Data.Text
import Text.RE.Replace
import Text.RE.TDFA.String

needle :: CaptureID
needle = IsCaptureName . CaptureName . pack $ "needle"

main :: IO ()
main = do
  re <- compileRegex "-${needle}([a-z]+)-"
  let match = "haystack contains the -word- you want" ?=~ re
  if matched match
  then print $ captureText needle match
  else print "(no match)"

Upvotes: 1

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