[Haskell-cafe] Bytestring map/zipWith rationale
Hello all, 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] ? Obviously they can be transformed into each other with pack/unpack, and as I understand it, the compiler performs sufficient optimizations so that there's no performance hit to doing things like (pack $ zipWith xor a b), but it still seems inconsistent. Is there a deep reason for this? -- Scott Lawrence Linux baidar 3.10.9-1-ARCH #1 SMP PREEMPT Wed Aug 21 13:49:35 CEST 2013 x86_64 GNU/Linux ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestring map/zipWith rationale
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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestring map/zipWith rationale
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? Tom ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestring map/zipWith rationale
On Thu, 12 Sep 2013 18:24:24 +0400, Tom Ellis tom-lists-haskell-cafe-2...@jaguarpaw.co.uk 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 why doesn’t map take “Word8 - a”, but only “Word8 - Word8”? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestring map/zipWith rationale
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 __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestring map/zipWith rationale
Carter: we don't have both. We have one function from each category. My guess is nobody's ever really needed a really fast zipWith :: (Word8-Word8-Word8) - ByteString - ByteString - ByteString; that's the only reason I can think of for its omission. On Thu, Sep 12, 2013 at 10:45 AM, Carter Schonwald carter.schonw...@gmail.com wrote: 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 __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestring map/zipWith rationale
I did use that a couple of times (`xor`ing 2 ByteStrings together), and was surprised by the omission back then, but IIRC (can't validate now), there's a specialised zipWith (as proposed) in the module (with some other name, obviously), which is not exported, but used when you 'pack' the result of 'zipWith' when the result is '[Word8]'... You might want to look into that. Nicolas On Sep 12, 2013 8:11 PM, John Lato jwl...@gmail.com wrote: Carter: we don't have both. We have one function from each category. My guess is nobody's ever really needed a really fast zipWith :: (Word8-Word8-Word8) - ByteString - ByteString - ByteString; that's the only reason I can think of for its omission. On Thu, Sep 12, 2013 at 10:45 AM, Carter Schonwald carter.schonw...@gmail.com wrote: 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 __**_ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/**mailman/listinfo/haskell-cafehttp://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Bytestring map/zipWith rationale
On Thu, Sep 12, 2013 at 12:44 PM, Nicolas Trangez nico...@incubaid.com wrote: I did use that a couple of times (`xor`ing 2 ByteStrings together), and was surprised by the omission back then, but IIRC (can't validate now), there's a specialised zipWith (as proposed) in the module (with some other name, obviously), which is not exported, but used when you 'pack' the result of 'zipWith' when the result is '[Word8]'... You might want to look into that. This is correct - there is a RULES pragma that rewrites `pack (zipWith f)` into a more efficient `zipWith'` function of the type desired (see the bytestring package). I was very concerned about this when writing lots of bytestring xor code for crypto-api and was pleased to find that, if the syntactic form matches, things get optimized as you desire. Thomas Nicolas On Sep 12, 2013 8:11 PM, John Lato jwl...@gmail.com wrote: Carter: we don't have both. We have one function from each category. My guess is nobody's ever really needed a really fast zipWith :: (Word8-Word8-Word8) - ByteString - ByteString - ByteString; that's the only reason I can think of for its omission. On Thu, Sep 12, 2013 at 10:45 AM, Carter Schonwald carter.schonw...@gmail.com wrote: 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
