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Visual Prolog
Visual Prolog IDE Screenshot.png
IDE Screenshot
Developer(s) Prolog Development Center
Stable release
7.5, Build 7502 / November 5, 2015; 17 months ago (2015-11-05)
Operating system MS Windows Vista/Windows 7/Windows 8
Type Programming language
License Proprietary

Visual Prolog, also formerly known as PDC Prolog and Turbo Prolog, is a strongly typed object-oriented extension of Prolog. As Turbo Prolog it was marketed by Borland, but it is now developed and marketed by the Danish firm Prolog Development Center (PDC) that originally developed it. Visual Prolog can build Microsoft Windows GUI-applications, console applications, DLLs (dynamic link libraries), and CGI-programs. It can also link to COM components and to databases by means of ODBC.

Logic languages are traditionally interpreted, but Visual Prolog is compiled. This provides the important improvement of converting traditional Prolog-typical run-time errors to compiler warnings, which ensures a better robustness of the finished applications.

The core of Visual Prolog are Horn clauses, algebraic datatypes, pattern matching and controlled non-determinism like in traditional Prolog, but unlike traditional Prolog, Visual Prolog has always been strongly and statically typed.


Brief Release HistoryEdit

Version 7.5 contains http server and LALR(1) parser generator (see also New Features in Visual Prolog 7.5).

Version 7.4 can generate 64 bit windows code (see also New Features in Visual Prolog 7.4).

Version 7.3 introduced generic classes and interfaces (see Generic programming), guarded monitors (see also New Features in Visual Prolog 7.3).

Version 7.2 introduced anonymous predicates (a logical pendant to anonymous functions) and namespaces (see also New Features in Visual Prolog 7.2).

Version 7.0 introduced parametric polymorphism.

Since version 6.0 the language has been fully object-oriented.

Hanoi ExampleEdit

In the 'Towers of Hanoi' example, the Prolog inference engine figures out how to move a stack of any number of progressively smaller disks, one at a time, from the left ('left') pole to the right pole ('right') in the described way, by means of a center ('center') pole as transit, so that there's never a bigger disk on top of a smaller disk. The predicate 'hanoi' takes an integer = the number of disks, as an initial argument. In real-life, Visual Prolog is especially suited for intricate problems, such as resource planning, etc. As the example shows, Visual Prolog can be used for quick 'programming in the small,' but it is mostly employed for industrial-strength large applications.

class hanoi 
       hanoi : (unsigned N). 
end class hanoi 
implement hanoi 
       pole = string. 
       hanoi(N) :- move(N, "left", "centre", "right"). 
   class predicates 
       move : (unsigned N, pole A, pole B, pole C). 
       move(0, _, _, _) :- !. 
       move(N, A, B, C) :- 
           move(N-1, A, C, B), 
           stdio::writef("move a disc from % pole to the % pole\n", A, C), 
           move(N-1, B, A, C). 
end implement hanoi 


BYTE in 1989 listed Turbo Prolog 2.0 as among the "Distinction" winners of the BYTE Awards, approving of how Borland had "developed a system for real-world applications programming".[1]

Visual Prolog Video TutorialsEdit

Books about Visual PrologEdit

See alsoEdit


  1. ^ "The BYTE Awards". BYTE. January 1989. p. 327. 

External linksEdit