ediprolog — Emacs does Interactive Prolog

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

The latest version of ediprolog is 1.2.
  • Atomic undo of the whole interaction (available in Emacs ≥ 26.1)

Download: ediprolog.el

Video demonstration: ediprolog.mpg (1MB)

For more information about Prolog development with Emacs, see PceProlog.
Factorial using CLP(FD)


To install ediprolog, copy ediprolog.el to your load-path, and add to your .emacs:
(require 'ediprolog)
(global-set-key [f10] 'ediprolog-dwim)
If F10 is not free on your platform, bind ediprolog-dwim to any other key sequence, for example, use:
(global-set-key "\C-c\C-e" 'ediprolog-dwim)
to bind it to C-c C-e. In the following, replace F10 with your custom binding.

Restart Emacs and use M-x customize-group RET ediprolog RET to configure ediprolog.


Queries in Prolog source files start with ?- or :-, possibly preceded by % and whitespace.

An example of a query is:
%?- member(X, [a,b,c]).
If you press F10 when point is on that query, you get:
%?- member(X, [a,b,c]).
%@ 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.

In transient mark mode, if the region is active, only the text in the region is consulted.

Other key sequences:

C-0 F10 kill Prolog process
C-1 F10 always consult buffer (even if 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 load buffer into existing process and then, if on a query, evaluate it
C-u C-u F10   like C-u F10, with a new process

Multi-line queries

ediprolog also supports multi-line queries. There are two ways to write a query that spans multiple lines in such a way that the meaning of the program is retained: To evaluate a multi-line query, invoke ediprolog-dwim on the first line of the query, which starts with ?-.

More about Prolog: The Power of Prolog

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