Page 1 of 1
Dynamic runtime predicate pointer binding
Posted: 28 Apr 2014 9:38
by kingchris
Pseudo Code.
Code: Select all
facts
predicate_pointer : pointer(string).
predicates
doNothing:(string).
writeToConsole:(string).
app_init().
doLotsOfWork().
clauses
app_init():-
if (debug_condition=true())
predicate_pointer := writeToConsole()
else
predicate_pointer := doNothing()
end if.
doLotsOfWork():-
repeat(),
LineVal = InStream:readLine(),
predicate_pointer(LineVal),
fail.
This is a contrived example of the kind of thing that I wish to do.
Can I set up a fact or property or domain to allow what could be called runtime binding so that either the doNothing predicate gets called or writeToConsole gets called based on a runtime test.
Thanks for your trouble
Posted: 28 Apr 2014 10:19
by Thomas Linder Puls
You must have gone to a wrong school before
.
You should not use a "predicate pointer" you should use a predicate:
Code: Select all
domains
writer = (string String).
facts
myWriter : writer.
predicates
doNothing:(string).
writeToConsole:(string).
app_init().
doLotsOfWork().
clauses
app_init():-
if debug_condition=true() then
myWriter := writeToConsole
else
myWriter := doNothing
end if.
doLotsOfWork():-
repeat(),
LineVal = InStream:readLine(),
myWriter(LineVal),
fail.
Also notice (other influence from your "wrong school") that you do not have to put parentheses around the test in an i-then-else, but you do have to write "then".
Posted: 28 Apr 2014 10:41
by kingchris
You are correct in your "wrong school" statements.
But please note that I did say Psuedo Code at the top. I and many other people on this forum, I am sure, program in multiple languages from F#, C#, C, C++, assembler, VB, Pascal etc. so its all gets very confusing. The latest PDC Prolog has introduced lots of things that you don't find in traditional Prolog. Hence I get very mixed up about what belongs in which language.
I was writing the essence of my problem. I personally get upset with people who post all of their code when asking a question. It becomes too much effort to read thorough and try and help them. So when I post a question I try keep it simple.
Thanks for your prompt answer.
I will code it up now into my program.
Cheers
Posted: 28 Apr 2014 14:26
by Thomas Linder Puls
No problem
.
I hope it solves your problem.