Re: [isabelle] efficient code for ('a, 'b) map (as opposed to ('a, 'b) mapping
The problem is, that ('a,'b) map is just syntactic sugar for the type
'a => 'b option. The code-generator replacement of types by efficient
implementations only works for types represented by a single
type-constant (like ('a,'b) mapping or 'a set).
Moreover, note that, in general, you do not want to translate all
occurences of "'a -> 'b option" by a map implementation, as there are
also functions that return option-values, which are intended to be
translated as functions.
The automatic refinement framework  tries to tackle this problem,
however, it has to be employed manually before code generation, and
usually requires some setup overhead.
In order to use Containers, I believe that you should transform your
functions to use mapping. Maybe the transfer+lifting package of Brian
and Ondra may help you to automate this task.
: Peter Lammich, Automatic Data Refinement, Proc. of ITP 2013
On Do, 2013-10-24 at 18:10 +0900, Christian Sternagel wrote:
> Dear all (especially Andreas ;)),
> is it possible to automatically get efficient code when code generating
> a function involving the "('a, 'b) map" type (i.e., "'a => 'b option").
> If I import AFP/Containers I can have this for "('a, 'b) mapping" (which
> is a type-copy of "('a, 'b) map").
> But in the actual formalization "('a, 'b) map" is more convenient to use
> since we have nice syntax like "m x" for lookup and "m (x |-> t)" for
> Since according to the user guide the above is possible w.r.t. "'a set",
> I was wondering what the obstacle is for "('a, 'b) map" (or maybe I just
> misunderstood something).
> More concretely, what is your advice for a function like
> match_list ::
> (('f, 'v) term * ('f, 'v) term) list =>
> ('v => ('f, 'v) term option) => ('f, 'v) subst
> where "match_list E Map.empty" gives a matcher for all equations in "E".
> Would you change this to use "('v, ('f, 'v) term) mapping" instead, or
> is there a way to get efficient code as it is? Thanks in advance!
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