Home/ Questions/Q 5951895
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-22T17:36:12+00:00

I appear to be having trouble creating a regular expression in Haskell, what I’m

  • 0

I appear to be having trouble creating a regular expression in Haskell, what I’m trying to do is convert this string (which matches a URL in a piece of text)

\b(((\S+)?)(@|mailto\:|(news|(ht|f)tp(s?))\://)\S+)\b

Into a regular expression, the trouble is I keep getting this error in ghci

Prelude Text.RegExp> let a = fromString "\b(((\S+)?)(@|mailto\:|(news|(ht|f)tp(s?))\://)\S+)\b"

<interactive>:1:27:
    lexical error in string/character literal at character 'S'

I’m guessing it’s failing because Haskell doesn’t understand \S as an escape code. Are there any ways to get around this?

In Scala you can surround a string with 3 double quotes, I was wondering if you could achieve something similar in Haskell?

Any help would be appreciated.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Every backslash in your string has to be written as a double backslash inside the double quotes. So

    "\\b(((\\S+)?)(@|mailto\\:|(news|(ht|f)tp(s?))\\://)\\S+)\\b"

    A more general remark: you’d be better off writing a proper parser rather than using regular expressions. Regular expressions rarely do exactly the right thing.

    • 0