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

[Jeffrey Brown]

Aha! Thanks, Kiss!

On Tue, Apr 5, 2016 at 1:24 PM, Adam Bergmark <adam at bergmark.nl> wrote:

> The regex-compat docs say "Returns: Just
> <https://hackage.haskell.org/packages/archive/base/4.5.0.0/doc/html/Data-Maybe.html#v:Just>
>  strs if the match succeeded (and strs is the list of subexpression
> matches), or Nothing
> <https://hackage.haskell.org/packages/archive/base/4.5.0.0/doc/html/Data-Maybe.html#v:Nothing>
>  otherwise.”.
>
> Adam Bergmark
>
>
> On Tue 05 Apr 2016 at 22:16 Jeffrey Brown <Jeffrey Brown
> <Jeffrey+Brown+%3Cjeffbrown.the at gmail.com%3E>> 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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>>
>
>


-- 
Jeffrey Benjamin Brown
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