[Haskell-beginners] Non-exhaustive patterns

[Jeffrey Brown]

It looks like your latest version works.

This also works:

*Temp> let replaceThe = unwords . map (\i -> if i=="the" then "a" else i) .
words
*Temp> replaceThe "is the bat"
"is a bat"
*Temp>


On Sat, Nov 18, 2017 at 10:46 AM, Brody Berg <brodyberg at gmail.com> wrote:

> My complete code:
>
> notThe :: String -> Maybe String
> notThe word
>   | word == "the" = Nothing
>   | otherwise     = Just word
>
> replaceThe :: String -> String
> replaceThe word = go $ words word
>   where
>     go []     = ""
>     go (x:xs) =
>           case (notThe x) of
>             Just x  -> x ++ " " ++ go xs
>             Nothing -> " a " ++ go xs
>
> On Sat, Nov 18, 2017 at 9:48 AM, Brody Berg <brodyberg at gmail.com> wrote:
>
>> Made some changes to replaceThe to handle the possibility of empty list:
>>
>> replaceThe :: String -> String
>> replaceThe word = go $ words word
>>    where
>>       go [] = “”
>>       go (x:xs) =
>>          case (notThe x) of
>>             Just x -> x ++ “ “ ++ go xs
>>             Nothing -> “ a “ ++ go xs
>>
>> Typed this on a phone, sorry
>>
>> On Sat, Nov 18, 2017 at 09:16 Jim <jimbo4350 at gmail.com> wrote:
>>
>>> Hey guys,
>>>
>>> Thiis is my function below:
>>>
>>> notThe :: String -> Maybe String
>>> notThe word
>>>        | word /= "the" = Just word
>>>        | word == [] = Just []
>>>        | otherwise = Nothing
>>>
>>> replaceThe :: String -> String
>>> replaceThe word = go (words word)
>>>        where go (x:xs)
>>>                | notThe x == Just [] = []
>>>                | notThe x == Just word = word ++ go xs
>>>                | notThe word == Nothing = " a " ++ go xs
>>>
>>>
>>>  > replaceThe "what"
>>> "what*** Exception: chap12.hs:(13,13)-(16,55): Non-exhaustive patterns
>>> in function go
>>>
>>> I thought I covered all the potential patterns in my replaceThe
>>> function. I'm not sure what pattern I've missed, any thoughts?
>>>
>>> Best regards,
>>>
>>> Jim
>>>
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>>>
>>
>
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