[Haskell-cafe] Bytestring map/zipWith rationale

[Scott Lawrence]

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