On Sun, Aug 10, 2014 at 09:07:42AM +0100, Malcolm Wallace wrote:
On 10 Aug 2014, at 07:04, Ivan Lazar Miljenovic wrote:
I'm +1 on the re-exporting (I would be tempted to go the whole hog and re-export all the Word* types as well).
I was involved in the discussions when the Word type was originally added to Haskell, primarily for the use of the FFI. As I recall, people were deeply uncomfortable that there should even be a Word type, with unspecified precision. The types Word8, Word16, Word32, and Word64 were entirely uncontroversial, because you know what you are dealing with. The primary use of the Word* types was to represent machine words (bytes, half-words, etc), enabling (for instance) bit-twiddling of individual components of the word. With an unknown-precision Word value, you can guarantee nothing about whether your bit-operation will work. I believe the use of unknown-precision Word to represent non-negative integers was the winning justification, but it remains controversial in the same way that Int (rather than Int32, or Integer) does. Lack of clarity over whether or when a number overflows is a pretty bad downside. Pragmatically, it may work OK for most people most of the time. But the Haskel l way is to prefer correctness.
I think I sympathise a great deal with people's discomfort. I feel like the ubiquity of Int was a mistake: it's basically a performance optimisation, with reasonably serious correctness issues, and shouldn't be the first thing every newbie comes across. I moreover feel like, e.g. `length :: [a] -> Word` (or things of that ilk) would be even more of a mistake, because type inference will spread that `Word` everywhere, and `2 - 3 :: Word` is catastrophically wrong. Although it seems nice to have an output type for non-negative functions that only has non-negative values, in fact Word happily supports subtraction, conversion from Integer, even negation (!) without a hint that anything has gone amiss. So I just don't believe that it is a type suitable for general "positive integer" applications. I feel a little unqualified to comment in the face of people far more knowledgeable and experienced than I am enthusiastically +1-ing this proposal, but I'm going to go ahead and -1 it. I think the situations in which Word is really what you want are few enough that it should not clutter the universal namespace.
Regards, Malcolm _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries