Re: [Caml-list] Expansion of type-constructors in ctype.ml

["Christoph Höger" <christoph.hoeger@tu-berlin.de>]

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Am 24.08.2015 um 00:18 schrieb Jacques Garrigue:
> This is indeed a pretty difficult problem, as you must be careful of not
> changing the semantics of unification.
> Until recently, the only solution was to expand the type, as there was
> no static information cacheing whether an argument was used in the
> body or not.
> However, since relatively recent changes about variance information
> (the switch to 7 flags…), we actually have at least an approximation
> of which unifications must be done imperatively, and which needn’t
> be done at all.
> So it might be doable at least for part of the parameters.

That sounds interesting. What are the relevant variance flags?

> I would have to see the code to tell you more.
> As stated above, the real problem is the length of the cycles in the expanded
> graph.

I really do not think that this is related to any cycles. It is just
about large unfolded types. I attached a script to generate a meaningful
example. When I try to run ocamlbuild m_9.cmo, it takes ~30s already. A
preliminary patched version of the ocaml compiler can handle this
particular example in pretty much no time at all.

regards,

Christoph

-- 
Christoph Höger

Technische Universität Berlin
Fakultät IV - Elektrotechnik und Informatik
Übersetzerbau und Programmiersprachen

Sekr. TEL12-2, Ernst-Reuter-Platz 7, 10587 Berlin

Tel.: +49 (30) 314-24890
E-Mail: christoph.hoeger@tu-berlin.de

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#!/usr/bin/env zsh

for ((i = 1 ; i < 10 ; i++)) ; do
  echo "class ['a] c (a : 'a) = object" > m_$i.ml
  echo "  method m_1 = (new M_$((i-1)).c) a#foo" >> m_$i.ml
  echo "  method m_2 = (new M_$((i-1)).c) a#foo" >> m_$i.ml
  echo "  method m_3 = (new M_$((i-1)).c) a#foo" >> m_$i.ml
  echo "  method m_4 = (new M_$((i-1)).c) a#foo" >> m_$i.ml
  echo "end" >> m_$i.ml
done

echo "class ['a] c (a : 'a) = object method m_1 = a#foo method m_2 = a#foo end" > m_0.ml