[Haskell-cafe] Bytestring map/zipWith rationale

[Carter Schonwald]

Scott: benchmark the two and you'll see why we have both :-)

On Thursday, September 12, 2013, Scott Lawrence wrote:

> On Thu, 12 Sep 2013, Tom Ellis wrote:
>
>  On Thu, Sep 12, 2013 at 09:21:20AM -0400, Scott Lawrence wrote:
>>
>>> Something's always bothered me about map and zipWith for ByteString. Why
>>> is it
>>>
>>>     map :: (Word8 -> Word8) -> ByteString -> ByteString
>>>
>>> but
>>>
>>>     zipWith :: (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
>>>
>>
>> Well, what if you wanted to zipWith a function of type "Word8 -> Word8 ->
>> Foo" instead of "Word8 -> Word8 -> Word8"?
>>
>
> Then I would do what I do with map, and call `unpack` first.
>
> Either of the two options is usable:
>
>  map :: (Word8 -> Word8) -> ByteString -> ByteString
>  zipWith :: (Word8 -> Word8 -> Word8) -> ByteString -> ByteString ->
> ByteString
>    (or)
>  map :: (Word8 -> a) -> ByteString -> [a]
>  zipWith :: (Word8 -> Word8 -> a) -> ByteString -> ByteString -> [a]
>
> I just don't understand why we have one from each.
>
> --
> Scott Lawrence
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