Copyright ( 1997-2013) EDMGROUP Pty Ltd - EZY Prolog Reference

EZY Dialogs

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EZY Prolog's dialog subsystem uses 2 major features:

  • External declarations of the GUI elements (DCL files created by EZY Designer)

  • EZY Prolog Virtual Machine (associated with dialog) which runs dialog prolog program

By use of Virtual Machine concept all predicates, declared in dialog control program, are encapsulated and not accessible outside of the dialog.

When dialog is created from DCL file, EZY Prolog:

  • compiles dialog prolog program into Dialog Virtual Machine, associated with dialog

  • calls initialize_gui clause to assign event handlers and initial values for the GUI elements.

Dialog Virtual Machine exists only when dialog is active and system removes all dialog-related code when dialog is closed.

By use of Virtual Machine concept system allow to have various dialogs with identical names of clauses (if programmer decided so). This prevents from redefinition of the predicates and keeps system consistent.

The EZY Dialog interface is very simple:

  • call ezy_dialog_create to create modal dialog and receive parameters when dialog is closed

  • call ezy_dialog_destroy to close dialog and define return parameters

  • call ezy_dialog_reply to get/set values of the GUI elements

See EZY dialog sample program for more information.


EZY Prolog supports primitive dialogs (similar to Visual Prolog):



Prompts user for a Yes/No response.


Creates listbox on the screen (see example)


Pop up a box containing a message Msg and OK button.


Activates dialog box to select a filename.


Activates dialog box to select a filename.


A dialog to prompt the user for a string response


Read the term through dialog exactly as read/1 does.


Sets the string text (help line) into the bottom of the current task window.




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