Re: [Haskell-cafe] Text.Regex.matchRegex: Success is empty?

Hi Jeffrey, It returns ‘Just’, because the pattern was found. The list is empty, because no capture groups are defined in the regex. matchRegex (mkRegex “(a)”) “abracadabra" returns Just [“a”] Csongor

On 5 Apr 2016, at 22:16, 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 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe