#VISUAL PROLOG 5.2 ONLINE CODE#
A not-so-obvious advantage of this code is that any Prolog interpeters written on the basis of Visual Prolog’s “PIE engine” (such as G.I.S.Jnz short if not zeroed, continue popping args. Pop edx recover next argument from the stackĭec ecx decrement the remaining number_of_args loop to POP function-args after the call Mov ecx, get the function's number of args from if the called function had NO args, exit 'fcnt'Ĭall ecx call the (external) function (given in ARG-1) = ,ebx store the number_of_args in local var. Jz short if so, not yet the list's end, so repeat! Lodsd load element-flag of next list-element Mov esi,eax now ESI = (pointer-to-) next list-element Lodsd load the pointer to next list-element in EAX Push eax push it into the stack (for a function-call) Inc ebx increment ebx (counter for number_of_args) loop to read the (Visual-Prolog-) arg-list Lodsd load the 1st list-element's "element-flag"ĭec al decrement it, to check if it was a 1 Mov ,ebx initialize local variable 'fcnt' to 0
C:\TASM\BIN\TASM32.EXE /p /z /w2 /m2 /ml _apply_func.asm IDEALĪLIGN 4 public _apply_func (i,i) PROC _apply_func near Code for TASM 5 Assembler, command-line call for compilation: OK, so here is the Assembly language code: = _apply_func.asm = %This program should produce " result = 60" (sum of ). % converts a predicate to a doubleword/addressįunc2dword(FUNC,DW):- DW = cast(dword,FUNC). % where arg-1 is a predicate-domain, such as "dom_iii"Īfter you compile the Assembly language code, you could create a simple “EasyWin” Visual Prolog project, with the following ines: PREDICATES
(i,i,i) language c % <- example domain GLOBAL PREDICATESĪpply_func(DWORD,ListDomain) -(i,i) language c However, before you (even begin to) look at the Assembly Language Code, the following simple definitions in Visual Prolog (5.*) are a prerequisite for easier understanding: GLOBAL DOMAINSĭom_iii = determ INTEGER (INTEGER,INTEGER,INTEGER) If you understand Assembly Language and intend to use this code for other (meta-programming) tasks, all you have to do is modify just a couple of lines in the code that follows. The only difference between the way it works for Visual Prolog and the way it might work for another Prolog (or -indeed- ANY programming language, using a ‘C’-calling convention) is the Visual-Prolog-specific structure of a LIST, which in Visual Prolog has a different form than in all other languages. However, this does not exist in Visual Prolog, which sacrifices such “luxuries” for speed (which is the reason I also often use ISO-Prolog compilers, such as LPA-WinProlog and SWI-Prolog).Īnyway… The code you are about to see can be useful more generally, as an example of Prolog meta-programming, implemented in Assembly Language. Now, in ISO-Prolog there is a standard predicate known as “univ”, written as “ =.“, which turns a list like into a predicate call such as PRED(ARG1,ARG2,…). here is an Assembly language predicate, that takes as inputs another (external) predicate’s memory-address and a ( Visual Prolog-) argument-list, and calls this (external) predicate, using the (arbitrary-length-) list of N arguments, as arguments of “arity N”:Īpply_func(PRED, ) PRED(Arg1,Arg2,…) They also have an intrinsic fascination in themselves, as general tools for Prolog meta-programming.Į.g. Prolog even further, potentially valuable for a multitude of other purposes. Recently, I discovered some Assembly language techniques to enhance G.I.S. Code modifications could therefore be done very quickly and most mistakes were (semi-)automatically corrected by the interpreter’s own enhanced error-checking capabilities.
Prolog produced immediate results, without any need for (often tedious) EXE-file compilation. Prolog for easy immediate experimentation: Coding in G.I.S. A multitude of extra predicates, implemented in pure Assembly language, became available through G.I.S. So, the only way to implement ISO-Prolog functionality in Visual Prologis to extend the “ PIE Interpreter” (and G.I.S. Of course, such attempts are inherently limited by the internal design of Visual Prolog compilers. Ever since I started using the Visual Prolog compilers (and the PDC Prolog compilers preceding them) I was fascinated by the possibilities of implementing additional ISO-Prolog functionality in Visual Prologthrough Assembly Language and ‘C’.
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