[Haskell-cafe] Stream fusion and span/break/group/init/tails
duncan.coutts at googlemail.com
Mon Apr 29 20:35:38 CEST 2013
On Mon, 2013-04-29 at 20:19 +0200, Gábor Lehel wrote:
> Thanks for the explanation. I looked at your thesis previously, but only
> read through a couple of sections (including the one about concatMap). I
> might go through the state machine parts as well now that I know the
> The thing in particular that was motivating me is that if it weren't for
> Skip, it seems that to some extent (I haven't had time to investigate
> precisely what extent) you could write a stream fusion framework in a
> datatype-generic way, parameterized over the base functor. But it wasn't
> obvious to me how (or whether) you would translate Skip. But maybe the
> state machine perspective will provide some insight into that. I'll think
> about it.
Oh I think you can write it in a data-type generic way.
If your datatype is described by a base functor F, then the skip version
is a simple transformation on that functor.
F_skip a = F a + a
And then the stream type for F is nu a. F_skip a
See section 3.6.
In most of my theory chapter I write it in this style, rather than using
the list functor specifically.
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