prolog 'call' not working properly

[NHALX]

Below is the output which fails under OS shen but works under PRO. The code generators for OS and Pro compile to the same code for 'test1'. I haven't looked closely at the code produced by test2, but they seem to be identical walls of text. Maybe lazyderef isn't working right?

Shen/OS

(4-)
(prolog? (test3 A B))
Z: (test1 Var2 Var3)
false

Shen/PRO

(4-) (prolog? (test3 A B))
Z: (test1 Var2 Var3)
testX->3: Var2
true

Code

(0-) (defprolog test1
  (mode 1 -) 2 <-- (prolog.trace "test1->2" 2);
  X 3          <-- (prolog.trace "testX->3" X);)
test1

(1-)
(defprolog test2
  A B [test1 A B] <--;)
test2

(2-)
(defprolog test3
  A B <-- (test2 A B Z)
          (prolog.trace "Z" Z)
          (call Z);)
test3

(3-) (defprolog prolog.trace
  Msg X <-- (when (do (output "~A: ~R~%" Msg X) true)); )
prolog.trace

[tizoc]

Just tested this and #58 in an older Shen (19.2) to make sure that the bug was not introduced in newer versions (because some changes have been made to the prolog code since), but it was a bug back then too.

This, along with #58 and #56 make me thing that SP has made a bunch of changes to the prolog code.

The prolog part of Shen is probably what I'm least familiar with, I will see if I can figure out #59 and #58 which seem pretty specific, and then ask Mark about #56.

[tizoc]

Ok, I was playing with this a bit, and something I noticed is that the generated code invokes call with the variable as is, without doing a deref on it, example:

(defun shen.f1296 (ProcN Cont)
  (let A (shen.newpv ProcN)
    (let B (shen.newpv ProcN)
      (let X (shen.newpv ProcN)
        (do (shen.incinfs)
          (bind X (cons test1 (cons 1 (cons (shen.deref A ProcN) (cons (shen.deref B ProcN) ()))))
                ProcN
                (freeze (call X ProcN Cont))))))))     \\ <---- here

but the definition of call looks like this:

(define call
  [F | X] ProcessN Continuation
  -> (call-help (function (lazyderef F ProcessN)) X ProcessN Continuation)
  _ _ _ -> false)

The generated code passes a prolog variable instead of something with the form [F | X], so the catch-all case gets it and returns false.

Can you tell me thats the generated code for this in SP?

(define something -> (prolog? (is X [test 1 A B]) (call X)))

I get this in the OS version:

(25-) (ps something)
[defun something [] [shen.f1296 [shen.start-new-prolog-process] [freeze true]]]

(26-) (ps shen.f1296)
[defun shen.f1296 [V1299 V1300] [let A [shen.newpv V1299] [let B [shen.newpv V1299] [let X [shen.newpv V1299] [do [shen.incinfs] [bind X [cons test [cons 1 [cons [shen.deref A V1299] [cons [shen.deref B V1299] []]]]] V1299 [freeze [call X V1299 V1300]]]]]]]]

[NHALX]

Shen, copyright (C) 2010-2015 Mark Tarver
www.shenlanguage.org, 18
running under Common Lisp, implementation: SBCL
port 2.1 ported by Mark Tarver
commercially licensed to Neal Alexander



(0-) (define something -> (prolog? (is X [test 1 A B]) (call X)))
something

(1-) (ps something)

[defun something [] 
  [let NPP [shen.start-new-prolog-process] 
     [let A [shen.newpv NPP] 
        [let B [shen.newpv NPP] 
           [let X [shen.newpv NPP] 
              [bind X [cons test 
                            [cons 1 [cons [shen.deref A NPP] 
                                          [cons [shen.deref B NPP] []]]]] 
                    NPP 
                    [freeze 
                     [call X NPP 
                           [freeze true]]]]]]]]]

It's basically the same minus the extra function def. Maybe the implementation of call does the dereference in SP.

[tizoc]

Yes, thats what I was guessing, but wanted to be sure, thank you.

[tizoc]

Ok, it works with a modified call function:

Shen, copyright (C) 2010-2015 Mark Tarver
www.shenlanguage.org, Shen 21
running under Scheme, implementation: chez-scheme
port 0.17 ported by Bruno Deferrari


(0-) (defprolog test1
  (mode 1 -) 2 <-- (prolog.trace "test1->2" 2);
  X 3          <-- (prolog.trace "testX->3" X);)
test1

(1-) (defprolog test2
  A B [test1 A B] <--;)
test2

(2-) 
(defprolog test3
  A B <-- (test2 A B Z)
          (prolog.trace "Z" Z)
          (call Z);)
test3

(3-) 
(defprolog prolog.trace
  Msg X <-- (when (do (output "~A: ~R~%" Msg X) true)); )
prolog.trace

(4-) (prolog? (test3 A B))
Z: (test1 Var2 Var3)
testX->3: Var2
true

[NHALX]

Nice job, thanks.

[rkoeninger]

Fixed by #60

@tizoc if you use the exact phrasing Fixes #XXX in the body of your PR description (not the title, the first comment), GitHub will automatically close the issue when you merge the PR.