primitive library

[Andrew Martin]

I'll get something together soon that explains my motivations. The short
summary is that the types in primitive unpack better that their
counterparts in vector (meaning, they unpack into one machine word instead
of three). I started using these types in internal data structures in
libraries I would write (since I didn't need slicing), and then just
started noticing stuff I thought it would be nice to add.

David noticed that a bunch of the typeclass instances were broken. I'd been
working on a library quickcheck-classes that I use to test instances at my
work place. The primitive library was missing a test suite, so I used it to
test all the instances to ensure that the fixes David had written were
correct. In the process, I found more broken instances and fixed them. The
life lesson here is that property testing is important.

PrimArray is an interesting story. Both winterland1989 and I had
independently written libraries that did the same exact thing: implement a
typed interface to ByteArray that keeps track of the element type. This
makes PrimArray much safer to work with than ByteArray. Eventually,
winterland's initial PR to bring this to primitive stalled. It implemented
several other features (some of which may still eventually get added), but
it's scope was large enough that no maintainer was able to feel comfortable
approving it. More recently, I took at stab at doing the same thing, but I
only added PrimArray, and after a lot of feedback from David, Carter, and
Ryan, it got merged in.

This got longer than I thought it would. I'll work on something that talks
more about motivations and features soon.

Andrew, David
I’ve seen a lot of traffic about the *primitive* library, in which you
two are playing a leading role.
Clearly something interesting is going on, but I have not been paying
enough attention to work out what. Maybe lots of unrelated things? Maybe
a handful of closely related things?
Would you consider putting out a summary (to libraries and ghc-devs) to
give an overview of the main threads, and any driving motivations. Why has
all this blown up now?
Meanwhile, thank you for being so active.
Simon

[David Feuer]

I think the areas in the primitive library demonstrate a part of the array
design space that seems to have gone relatively unexplored in Haskell:
plain old vectors. Unlike the vector library, there is no stream fusion
framework. Unlike the array library, there is no class-based reliance on
fold/build fusion.

The (flawed) addition of numerous class instances a couple versions ago
made primitive arrays seem much more viable to end users as an alternative
to their heavier counterparts. I have become interested in fixing the
mistakes that were made, seeing just how much performance we can squeeze
out (and what limitations we run into), and fleshing out the API.

Post by Andrew Martin
I'll get something together soon that explains my motivations. The short
summary is that the types in primitive unpack better that their
counterparts in vector (meaning, they unpack into one machine word instead
of three). I started using these types in internal data structures in
libraries I would write (since I didn't need slicing), and then just
started noticing stuff I thought it would be nice to add.
David noticed that a bunch of the typeclass instances were broken. I'd
been working on a library quickcheck-classes that I use to test instances
at my work place. The primitive library was missing a test suite, so I used
it to test all the instances to ensure that the fixes David had written
were correct. In the process, I found more broken instances and fixed them.
The life lesson here is that property testing is important.
PrimArray is an interesting story. Both winterland1989 and I had
independently written libraries that did the same exact thing: implement a
typed interface to ByteArray that keeps track of the element type. This
makes PrimArray much safer to work with than ByteArray. Eventually,
winterland's initial PR to bring this to primitive stalled. It implemented
several other features (some of which may still eventually get added), but
it's scope was large enough that no maintainer was able to feel comfortable
approving it. More recently, I took at stab at doing the same thing, but I
only added PrimArray, and after a lot of feedback from David, Carter, and
Ryan, it got merged in.
This got longer than I thought it would. I'll work on something that talks
more about motivations and features soon.

Andrew, David
I’ve seen a lot of traffic about the *primitive* library, in which you
two are playing a leading role.
Clearly something interesting is going on, but I have not been paying
enough attention to work out what. Maybe lots of unrelated things? Maybe
a handful of closely related things?
Would you consider putting out a summary (to libraries and ghc-devs) to
give an overview of the main threads, and any driving motivations. Why has
all this blown up now?
Meanwhile, thank you for being so active.
Simon

--
-Andrew Thaddeus Martin
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