3.5 How do I use eclipse?
3.5.1 Getting started
To start ECLiPSe, type the command eclipse at an
operating system command-line prompt.
This will display something like this:
The list in square brackets on the first line specifies the configuration
of the running system, i.e. the language extensions that are present.
The copyright and version information is followed by the prompt [eclipse 1]:, which tells the user that the top-level loop is waiting
for a user query in the module eclipse.
The predicate help/0 gives
general help and help/1 gives
help about specific built-in predicates.
ECLiPSe Constraint Logic Programming System [kernel]
Kernel and basic libraries copyright Cisco Technology Inc
Academic licensing through Imperial College London, see legal/licence_acad.txt
GMP library copyright Free Software Foundation, see legal/lgpl.txt
For other libraries see their individual copyright notices
Version X.Y #Z, DAY MONTH DD HH:MM YYYY
3.5.2 Interacting with the top level loop
The ECLiPSe prompt [eclipse 1]: indicates that ECLiPSe
is at the top level
and the opened module is eclipse.
The top level loop is a procedure which repetitively
prompts the user for a query, executes it and reports its
result, i.e. either the answer variable bindings or the
There is always exactly one module opened in the top level
and its name is printed in the prompt.
From this point it is possible to enter ECLiPSe goals, e.g. to
pose queries, to enter an ECLiPSe program from the keyboard
or to compile a program from a file.
Goals are entered after the prompt and are terminated by full stop and
The ECLiPSe system may be exited by typing CTRL-D (UNIX) or
CTRL-Z + RETURN (Windows) at the top level prompt,
or by calling either the halt/0
or the exit/1 predicates.
3.5.3 Compiling a program
The square brackets [...] or the
compile/1 predicate are used
to compile ECLiPSe source from a file.
If the goal
or the short-hand notation
is called, either as a query at the top level or within another goal,
the system looks for the file myfile or for a file called myfile.pl or myfile.ecl and compiles it.
The short-hand notation may also be used to compile several files in
The compile/2 predicate may be used to compile a file or list of
files into a module specified in the second argument.
[ file_1, file_2, ..., file_n ]
If a file has been modified since it was compiled, it may be recompiled by
invoking the make/0 predicate.
This recompiles any files which have become out-of-date.
For more information on program compilation and the compiler, please see
3.5.4 Entering a program from the terminal
Programs can be entered directly from the terminal, as well as being read
To do this, simply compile the special file user.
That is, [user]. or compile(user). at a top level
The system then displays the compiler prompt (which is a blank by default)
and waits for a sequence of clauses.
Each of the clauses is terminated by a full stop.
(If the fullstop is omitted the system just sits
waiting, because it supposes the clause is not terminated.
If you omit the stop by accident simply type it in on the following line,
and then proceed to type in the program clauses, each followed by a full
stop and carriage return.)
To return to the top level prompt,
type CTRL-D (UNIX), CTRL-Z + RETURN (Windows) or enter the atom
end_of_file followed by fullstop and RETURN.
The two predicates father/2 and ancestor/2 are now compiled
and can be used.
[eclipse 1]: [user].
ancestor(X, Y) :- father(X, Y).
ancestor(X, Y) :- ancestor(X, Z), ancestor(Z, Y).
user compiled traceable 516 bytes in 0.00 seconds
3.5.5 Executing a query
Once a set of clauses has been compiled,
it may be queried in the usual Prolog manner.
If there are no uninstantiated variables in the query, the system
replies 'yes' or 'no' and prompts for another query, for example:
If there are uninstantiated variables in the query,
the system will attempt to find an instantiation of them which will
satisfy the query, and if successful it will
display one such instantiation.
It will then wait for a further instruction: either a
[eclipse 1]: father(jacob, joseph).
(“newline” or “return”) or a semi-colon ';'.
A return will end the query successfully.
A semi-colon will initiate backtracking
in an attempt to find another solution to the query.
Note that it is not necessary to type a new line after the semicolon
— one keystroke is enough.
When the top level loop can detect
that there are no further solutions, it does not wait for the semicolon
or newline, but it displays directly the next prompt.
For example in a query on
a family database:
Queries may be extended over more than one line. When this is done the prompt
changes to a tabulation character, i.e. the input is indented to
indicate that the query is not yet completed.
The fullstop marks the end of the input.
[eclipse 2]: father(X, Y).
X = abraham
Y = isaac More? (;) (';' typed)
X = isaac
Y = jacob
3.5.6 Interrupting the execution
If a program is executing, it may be interrupted by
typing CTRL-C (interrupt in the UNIX environment).
This will invoke the corresponding interrupt handler
(see section 13.3).
By default, the system prints a menu offering some alternatives:
The a option returns to the toplevel, b starts a nested toplevel,
c continues the interrupted execution, d switches the debugger
to creep mode (provided it is running), and e is an emergency exit
of the whole ECLiPSe session.
interruption: type a, b, c, e, or h for help : ? help
a : abort
b : break level
c : continue
e : exit
h : help
interruption: type a, b, c, e, or h for help : ?
The execution of ECLiPSe may be suspended by typing CTRL-Z
(suspend) or by calling pause/0.
This will suspend the ECLiPSe process and return the UNIX prompt.
Entering the shell command fg will return to ECLiPSe.
Note that this feature may not be available on all systems.
3.5.7 Debugging a program
Please see the chapters on debugging in the tutorial and user manuals for
more details. The tutorial chapter covers the TkECLiPSe debugging in a
tutorial style tour, and the user manual chapter covers
general and the command-line debugger in particular.
3.5.8 The history mechanism
The ECLiPSe toplevel loop provides a simple history mechanism which allows
the examination and repetition of previous queries.
The history list is printed with the command h.
A previous query is invoked by typing either its absolute number or its
relative negative offset from the current query number (i.e. –1 will
execute the previous query).
The current query number is displayed in the toplevel prompt.
The history is initialized from the file .eclipse_history
in the current directory or in the home directory.
This file contains the history goals, each ended by a fullstop.
The current history can be written using the predicate
write_history/0 from the
3.5.9 Getting help
Detailed documentation about all the predicates in the ECLiPSe libraries
can be obtained online through the help facility.
It has two modes of operation.
First, when a fragment of a built-in name is specified, a list of short
descriptions of all built-ins whose name contains the specified string
will print one-line descriptions about write/1, writeclause/2, etc.
When a unique specification is given, the full description of the
specified built-in is displayed, e.g. in