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Program Development Tools

Next to using any editor capable of editing plain text files and running SWI-Prolog in a separate window there are several options to improve the user experience for the regular Prolog programmer.

SWI-Prolog native development tools

Built-in tools

The built-in tools provide a feature rich environment for developing with SWI-Prolog. The tools are built on top of the portable XPCE graphics system. They look outdated and the learning curve for the built-in Emacs clone is steep. The real-time semantic highlighting greatly reduces the number of bugs you need to fix after writing your program and the context menu on predicates and goals make it easy to navigate your code.

  • PceEmacs.md is a GNU-Emacs clone in XPCE/Prolog, providing Prolog syntax highlighting based on parsing and cross-referencing the editor buffer. Colouring highlights variables, quoted entities, comments, goals (classified as built-in, imported, local, dynamic and undefined), predicates (classified as local, public and unreferenced), and file references (classified as existent/non-existent). PceEmacs is started using the predicates emacs/0, edit/0 or edit/1.

    Similar functionality is now provided for GNU-Emacs using the sweep. See below

  • The graphical tracer provides source-level debugging, using three views: your source, variable bindings, and the stack. The stack view includes choicepoints and visualises the effect of executing the cut!
  • The Execution Profiler provides a graphical overview of call and time statistics.
  • The Cross Referencer analyzes dependencies in the loaded program and points out undefined and unused code. It can also generate module headers and import directives based on the analysis.
  • The Prolog Navigator provides an explorer-like view on a directory holding Prolog source files. Sources files can be expanded in the tree to show predicates, exports, XPCE classes and methods. Can be used to edit entities or enable debugging them (spy).

Both the Windows Prolog console swipl-win.exe and the app for MacOSX (swipl-win) provides a menu to access many of these facilities directly.

We intend to allow the user to select preferred tools and combine them with whatever they like. In other words, we don't want to force the user into using a bulky all-in-one closed toolkit.

SWISH (web based Prolog)

SWISH provides a web-based tool for running Prolog. It provides a CodeMirror based editor with server-enriched semantic highlighting based on the same library as the above mentioned built-in editor. SWISH can display Prolog results as tables, charts and anything supported by HTML5 and JavaScript. SWISH notebooks provide functionality inspired by Jupyter/IPython notebook.

SWISH provides a smooth transition starting with conventional Prolog programs using text output. Next, HTML5 output can be added. Workflows, tutorials, etc. can be written as notebooks that mix text, queries and program fragments as well as embedded web applications that provide a rich experience to non-programmers.

SWISH can run in several configurations.

  • As a public server it can be used to run harmless queries against a Prolog itself or a read-only database.
  • It can be installed with authentication enabled, which allows for running arbitrary Prolog programs.
  • Mixed, where non-authenticated users can run harmless queries and authenticated users can run anything.

SWI-Prolog Editor (Windows)

Gerhard Röhner has developed an integrated Prolog editor in MS-Windows following the conventions of this platform. The embedded SWI-Prolog provides functionality similar to swipl-win.exe, including the possibility to run XPCE GUI programs.

Especially for classroom usage on MS-Windows, you should consider this version. The site also contains some demo material.

Support in standard editors

The lack of keywords, existence of dynamic operator declarations (see op/3), macro expansion and meta-calling make Prolog a difficult language for generic editors and IDEs. On the other hand, switching between editors is hard and thus most people like using one editor for all their tasks. Below are plugins for generic editors that we are aware of. Please let us know if you know other plugins.

Using GNU-Emacs

Unfortunately, standard GNU-Emacs Prolog mode is very weak, especially at handling proper Prolog indentation. The good news is that there is good Emacs Prolog mode available as sweep. This mode is similar to the built-in PceEmacs. The mode replies on embedding SWI-Prolog as an Emacs module. The required foreign library is bundled with the binary distributions of Prolog. Requires SWI-Prolog 8.5.20 or later.

Eclipse based

Prolog Development Tool - PDT
The PDT is a Prolog IDE provided as a plug-in for the Eclipse Platform. All PDT features are implemented for SWI-Prolog, most also for Logtalk). All native SWI-Prolog development tools (graphical tracer / debugger, profiler, ...) can be used within the PDT.
Prolog Development Tools - ProDT
Prolog Development Tools (ProDT) is a Prolog Integrated Development Environment (IDE) aiming to be as rich in functionality as the Eclipse's java IDE, giving the developer a single environment where it can control the development of a Prolog project from code edition, test execution, debugging, and more...