The regex-compat docs say "Returns: Just strs if the match succeeded (and strs is the list of subexpression matches), or Nothing otherwise.”.

Adam Bergmark

On Tue 05 Apr 2016 at 22:16 Jeffrey Brown <Jeffrey Brown > wrote:

Esteemed Haskellers,

It is working for me, but I am puzzled by the matchRegex function:

    > import Text.Regex

    > :i matchRegex

    matchRegex :: Regex -> String -> Maybe [String]

            -- Defined in ‘Text.Regex’

Searches that fail return Nothing:

    > matchRegex (mkRegex "z") "abracadabra"

    Nothing

which makes sense. But why do searches that succeed return an empty list of Strings?

    > matchRegex (mkRegex "a") "abracadabra"

    Just []

    > 

--

Jeffrey Benjamin Brown

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