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https://github.com/triska/ediprolog

Emacs Does Interactive Prolog
https://github.com/triska/ediprolog

emacs emacs-lisp prolog prolog-process

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Emacs Does Interactive Prolog

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# 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/**](https://www.metalevel.at/ediprolog/)



**Video**:



[https://www.metalevel.at/prolog/videos/ediprolog](https://www.metalevel.at/prolog/videos/ediprolog)



See also [PceProlog](https://www.metalevel.at/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](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](https://www.metalevel.at/prolog/clpz) to

relate a number to its factorial:



![Factorial](factorial.png)