yap-6.3/Logtalk/examples/operators/SCRIPT.txt

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Logtalk - Object oriented extension to Prolog
Release 2.29.5

Copyright (c) 1998-2007 Paulo Moura.  All Rights Reserved.
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% start by loading the example:

| ?- logtalk_load(operators(loader)).
...


% operators declared inside an object are not visible outside:

| ?- double::(I double J).

Syntax error: Operator expected


% you must use instead functor notation:

| ?- double::double(I, J).

I = 1
J = 2 ;

I = 2
J = 4 ;

I = 3
J = 6 

yes


% operators also affect inputing of terms, enabling this example to work:

| ?- triple::triple(I, J).

I = 1
J = 3 ;

I = 2
J = 6 ;

I = 3
J = 9 

yes


% check the file "previous.txt" generated from the file "next.txt" by the object "reverse"
% by opening the files on a text editor


% the "edge" operator on the "local.lgt" source file is not globally visible:

| ?- graph1::(N1 edge N2).
uncaught exception: error(syntax_error('user_input:10 (char:13) ) or operator expected'),read_term/3)


% you must use instead functor notation:

| ?- graph1::edge(N1, N2).

N1 = a
N2 = b ;

N1 = a
N2 = c ;

N1 = b
N2 = d ;

N1 = c
N2 = d

yes


| ?- graph1::path(a, d, Path).

Path = [a, b, d] ;

Path = [a, c, d] 

yes


% confirm that the "edge" operator have not became global:

| ?- current_op(P, T, edge).

no