Shen Prolog to get ASSERT and RETRACT

[Mark Tarver]

I've been limping along with the FTP and trying to work

around not having ASSERT and RETRACT.  However the

results are not satisfactory.  I think I have a method of

introducing these features into Shen Prolog which is 

reasonably efficient (RETRACT will be very fast).

If successful this will be the second time that Shen Prolog

has been upgraded via the FTP.  It was humungous size

of FTP computations that forced the development of a

Prolog garbage collector for the S series kernel.  Prior to this

a Shen Prolog computation could only run for a few seconds.

Mark

[Mark Tarver]

ASSERT is in place.

(2-) (dynamic f)
[f]

(3-) (defprolog f
       b <--;)
(fn f)

(4-) (time (asserta [[f a] <--]))
run time: 0.015600100000000117 secs
(fn fA)

(5-) (prolog? (f a))
true

Next RETRACT.

Mark

[Mark Tarver]

ASSERT is constant time wrt to whatever code is attached to f.

Mark

[nha...@gmail.com]

'declare' and the sequent compiler might as well use assert too.

[Mark Tarver]

Shen, www.shenlanguage.org, copyright (C) 2010-2022, Mark Tarver
version: S34, language: Common Lisp, platform: SBCL 2.0.0
port 3.2, ported by Mark Tarver

(0-) (time (prolog? (asserta [[f a] <--;])))
run time: 0.015000000596046448 secs
true

(1-) (prolog? (f a))
true

(2-) (time (prolog? (retract [[f a] <--;])))
run time: 0.0 secs
true

(3-) (prolog? (f a))
false

retract just involves changing the value returned by  a pointer and 

does not invoke the Prolog compiler.  Ergo the speed.

Mark

[Mark Tarver]

On Wednesday, 21 September 2022 at 22:42:44 UTC+1 nha...@gmail.com wrote:

'declare' and the sequent compiler might as well use assert too.

Well you have include and preclude for type theories.

M. 

[nha...@gmail.com]

For the Chez/SWI backend of Shen I have t-star call shen.lookupsig directly,  and the implementation of 'declare'  just asserts and retracts as needed.

Seems much more straightforward, and probably faster on this particular port due to FFI overhead. 

[Mark Tarver]

Seems sensible, you can also have overloaded types that way.

M.