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Asked: 2026-05-27T12:27:54+00:00

I’m having some trouble with regexes in haskell. Specifically: Prelude Text.Regex.Posix> 1 =~ \d

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I’m having some trouble with regexes in haskell. Specifically:

Prelude Text.Regex.Posix> "1" =~ "\d" :: Bool
<interactive>:1:10:
    lexical error in string/character literal at character 'd'
Prelude Text.Regex.Posix> "1" =~ "\\d" :: Bool
False
Prelude Text.Regex.Posix> "1" =~ "\\\\d" :: Bool
False

Does Haskell not have the \d or \s or other such convenient escape codes? Yes, I know I can do [0-9] instead, but the escape codes can be so much more convienient for complex regexes. Am I missing something obvious here?

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  1. Editorial Team

    I don’t know much about the Haskell regex packages, but from your examples above with “Text.Regex.Posix”, I might infer that you’re dealing in POSIX regular expressions. Escape sequences such as \d and \s aren’t part of POSIX regex syntax, and I believe originated with Perl and have since propagated into other languages.

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