[Ecls-list] [Suggestion] Caching expansion of type-specifier

[Juan Jose Garcia-Ripoll]

On Sun, Nov 29, 2009 at 7:00 PM, Gabriel Dos Reis
<gdr at integrable-solutions.net> wrote:
> On Sun, Nov 29, 2009 at 10:29 AM, Juan Jose Garcia-Ripoll
> <juanjose.garciaripoll at googlemail.com> wrote:
>> How can ECL decide to cache a DEFTYPE form? I mean, the following is
>> utterly absurd, but it may well happen:
>>
>> (deftype foo () (declare (special *foo-expansion*)) *foo-expansion*)
>
> Could not ECL keep a cache of a conservatively approximated side-effect
> free deftypes?  For example, any reference to a special variable or non
> constant could qualify for non-side-effect free.
>
> Even the general thing could be very complicated, there are some
> low-hanging fruits to have...

The problem is more general: right now we do not have an
infrastructure to tell functions that have side effects from functions
that do not. Even SBCL has this problem right now: it caches without
caring much about the type itself
* (defvar *foo-expansion* 'integer)

*FOO-EXPANSION*
* (deftype foo () *foo-expansion*)
FOO
* (subtypep 'fixnum 'foo)
T
T
* (setf *foo-expansion* 'string)
STRING
* (subtypep 'fixnum 'foo)
T
T

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Instituto de Física Fundamental, CSIC
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