Introduction

ediprolog lets you interact with Prolog in all Emacs buffers. You can consult Prolog programs and evaluate embedded queries.

Project page:

https://www.metalevel.at/ediprolog/

Video:

https://www.metalevel.at/prolog/videos/ediprolog

See also PceProlog.

Installation

With Emacs≥24.1, the simplest way to install ediprolog is to use Emacs's built-in package manager via the key sequence:

M-x package-install RET ediprolog RET

Alternatively, copy ediprolog.el to your load-path and add the following form to your .emacs, then evaluate the form or restart Emacs:

(require 'ediprolog)

After you have installed ediprolog, you can customize it with:

M-x customize-group RET ediprolog RET

The two most important configuration options are:

• ediprolog-system, either scryer (default) or swi
• ediprolog-program, the path of the Prolog executable.

Usage

The central function is ediprolog-dwim (Do What I Mean). I recommend to bind it to the function key F10 by adding the following form to your .emacs and evaluating it:

(global-set-key [f10] 'ediprolog-dwim)

In the following, I assume that you have also done this.

Depending on the content at point, ediprolog-dwim does the "appropriate" thing: If point is on a query, it sends the query to a Prolog process, and you interact with the process in the current buffer as on a terminal. Queries start with "?-" or ":-", possibly preceded by "%" and whitespace. An example of a query is:

%?- member(X, "abc").

If you press F10 when point is on that query, you get:

%?- member(X, "abc").
%@    X = a
%@ ;  X = b
%@ ;  X = c
%@ ;  false.

When waiting for output of the Prolog process, you can press C-g to unblock Emacs and continue with other work. To resume interaction with the Prolog process, use M-x ediprolog-toplevel RET.

If you press F10 when point is not on a query, the buffer content is consulted in the Prolog process, and point is moved to the first error (if any). You do not need to save the file beforehand, since the buffer content (not the file) is consulted.

For convenience, the most recent interactions with the Prolog process are logged in the buffer *ediprolog-history*.

Use M-x ediprolog-localize RET to make any Prolog process started in the current buffer buffer-local. This way, you can run distinct processes simultaneously. Revert with M-x ediprolog-unlocalize RET.

ediprolog-dwim with prefix arguments has special meanings:

Key Sequence	Meaning
C-0 F10	kill Prolog process
C-1 F10	always consult buffer (even when point is on a query)
C-2 F10	always consult buffer, using a new process
C-7 F10	equivalent to `ediprolog-toplevel'
C-u F10	first consult buffer, then evaluate query (if any)
C-u C-u F10	like C-u F10, with a new process

Tested with Scryer Prolog 0.8.119 and SWI-Prolog 8.1.24, using Emacs versions 26.1 and 27.0.50.

Screenshot

Here is a sample interaction, using CLP(ℤ) constraints to relate a number to its factorial: