The behavior of the Emacs interface can be controlled by a set of user-configurable settings. Some of these can be changed on the fly, while some require Emacs to be restarted. To set a variable on the fly, type M-x set-variable RET VariableName RET Value RET. Note that variable names can be completed by typing a few characters and then pressing TAB.
To set a variable so that the setting is used every time Emacs is started, add lines of the following format to ~/.emacs:
(setq VariableName Value)
Note that the Emacs interface is presently not using the ‘Customize’ functionality to edit the settings.
The available settings are:
The Prolog system to use.
'sicstus, which will be assumed for the rest of this
chapter. See the on-line documentation for the meaning of other
settings. For other settings of
prolog-system the variables below
sicstus-something will not be used, in some cases
corresponding functionality is available through variables named
The version of SICStus that is used. Defaults to
'(4 . 2).
Note that the spaces are significant!
t (the default) to enable the source-linked debugging
extensions by default. The debugging can be enabled via the
Prolog menu even if this variable is
nil. Note that the
source-linked debugging only works if
How many positions to indent the body of a clause. Defaults
tab-width, normally 8.
The number of positions to indent code inside grouping parentheses. Defaults to 4, which gives the following indentation.
p :- ( q1 ; q2, q3 ).
Note that the spaces between the parentheses and the code are automatically inserted when TAB is pressed at those positions.
nil to prevent single
%-comments from being automatically
aligned. Defaults to
Note that comments with one
% are indented to comment-column, comments
% to the code level, and that comments with three
never changed when indenting.
nil to prevent indentation of text inside
… */ comments. Defaults
This is a list with keywords that are highlighted in a special color
when used as directives (i.e. as
keyword). Defaults to
'("block" "discontiguous" "dynamic" "initialization" "meta_predicate" "mode" "module" "multifile" "public" "volatile" "det" "nondet" ; for spdet )
nil to prevent Emacs from automatically indenting the next
line when pressing RET. Defaults to
t to enable deletion of all whitespace before the
cursor when pressing DEL (unless inside a comment, string,
or quoted atom). Defaults to
t to enable the electric dot function. If enabled,
pressing . at the end of a non-empty line inserts a dot and a
newline. When pressed at the beginning of a line, a new head of
the last predicate is inserted. When pressed at the end of a line
with only whitespace, a recursive call to the current predicate is
inserted. The function respects the arity of the predicate
and inserts parentheses and the correct number of commas for separation
of the arguments. Defaults to
t to enable the electric underscore function. When
enabled, pressing underscore (_) when the cursor is on a
variable, replaces the variable with the anynomous variable. Defaults to
nil to use built-in functions of Emacs for parsing the
source code when indenting. This is faster than the default but
does not handle some of the syntax peculiarities of
Prolog. Defaults to
What position the parsing is done from when indenting code. Two possible
'beg-of-clause. The first is
faster but may result in erroneous indentation in
/* … */
comments. The default is
t to enable a new
Predicate menu that contains all
predicates of the current file. Choosing an entry in the menu
moves the cursor to the start of that predicate. Defaults to
The info node for the SICStus predicate index. This is important
if the online help function is to be used (by pressing C-c ?, or
Prolog/Help on predicate menu entry). The default
nil to not make underscore (_) a word-constituent
character. Defaults to
Font-locking uses a number of “faces”, which can be customized with regular Emacs commands, for instance M-x describe-face RET FaceName RET. The following faces are relevant:
highlight since release 4.2
Source code highlight at debug ports.
pltrace-face-reached-det since release 4.2
Highlight for a line of code reached by coverage analysis with no nondet calls made from that line of code.
pltrace-face-reached-nondet since release 4.2
Highlight for a line of code reached by coverage analysis with one or more nondet calls made from that line of code.
pltrace-face-reached-not since release 4.2
Highlight for a line of code not reached by coverage analysis.
prolog-warning-face since release 4.2
Face used in warning messages.
prolog-informational-face since release 4.2
Face used in informational messages.
prolog-exception-face since release 4.2
Face used in the first line of an error exception message, as well as to highlight Exception port displays.
prolog-error-face since release 4.2
Face used in other lines of exception messages.
prolog-call-face since release 4.2
Face used to highlight Call port displays.
prolog-exit-face since release 4.2
Face used to highlight Exit port displays.
prolog-redo-face since release 4.2
Face used to highlight Redo port displays.
prolog-fail-face since release 4.2
Face used to highlight Fail port displays.
prolog-builtin-face since release 4.2
Face used to highlight keywords used in directives (see