Visual prolog example programs

The code differs from the standard one only in terms stdio::write to write the message to the console and programControl::sleep to pause program execution.

In main. Keyword procedure describes the behavior of predicate, indicating that is will always succeed with only one solution, so no backtracking is required. There are two possible matches for each call of factorial — with zero or arbitrary first argument.

Visual Prolog searches the clauses for matching call in the order of their appearance in the code, so if first argument is zero, it starts with first clause factorial 0,F. It also illustrates that facts databases can be written to any outputStream. Sudoku A currently very popular logical Sudoku puzzle is used as an example. We show how such a problem can be solved using constraint programming and explain a simple approach to finite domains constraint solving. Furthermore, we show how to build an interactive GUI that visualizes the workings of the constraint solver.

Validation is usually a check, which is performed on pressing OK button. Such check makes sure that all necessary controls with input values contains valid values. In the Office subdirectory there is an example of a DDE client applications, which can communicate with Microsoft Office programs.

With the MS Word, for example. GridForm This example demonstrates how to can create grid controls. Reference Variables. Declaring Domains as Reference. Reference Domains and the Trail Array. Using Reference Domains. Flow Patterns Revisited. Using Binary Trees with Reference Domains. Sorting with Reference Domains. Functions and Return Values.

Determinism Monitoring in Visual Prolog. Visual Prologs determinism checking system. Predicates as Arguments. Predicate Domains. The Binary Domain. Implementation of binary terms. Text syntax of Binary Terms. Creating Binary Terms. Accessing Binary Terms. Unifying Binary Terms. Converting Terms to Binary Terms. Errors and Exception Handling. Exception Handling and Error Trapping. Error reporting. Handling Errors from the Term Reader.

Break Control Textmode Only. Dynamic Cutting. Free Type Conversions. Programming Style. Rules for Efficient Programming. Determinism vs. Non-determinism: Setting the Cut. Writing and Reading. Binary Block Transfer. Visual Prolog's File System. Opening and Closing Files. Working with Files. File Attributes. File and Path Names. Directory Searching. Manipulating File Attributes. Handling terms in text files. Manipulating Facts Like Terms. String Processing. Basic String-Handling Predicates.

Type Conversion. External Databases in Visual Prolog. An Overview: What's in an External Database? External Database Domains. Manipulating Whole External Databases. Manipulating Chains. Manipulating Terms. A Complete Program Example. Pages, Order, and Keylength. Duplicate Keys. Multiple Scans. External Database Programming. Scanning through a Database. Displaying the Contents of a Database. Updating the Database. Changing the Structure of a Database. Filesharing and the External Database.

Filesharing Domains. Opening the Database in Sharemode. Programming with Filesharing. Implementing highlevel locking. A Complete Filesharing Example.

Implementation Aspects of Visual Prolog Filesharing. Access to the operating system. Timing Services. Bit-Level Operations. Notice that the line starts with a :- and ends with a period. Now let's skip to the "main" function. For this first simple example, we'll just give the user the choices to run a query or quit. Finally, we call main again so that we keep displaying the menu until we're done.

And finally we have the predicates that actually do the work. Here we want to run a query that the user inputs. We'll also call a couple of predicates that we haven't defined yet to print out the results of our query. We'll get to those definitions shortly. Notice that the first definition just has the number 1 as the parameter.

That's because 1 was the menu option for running a query. And we're almost done!