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operators

This folder contains examples of using operators inside objects and categories:

[100, 111, 117, 98, 108, 101, 46, 108, 103, 116]

Simple object containing clauses using an infix operator.

[116, 114, 105, 112, 108, 101, 46, 108, 103, 116]

Simple object reading from a file, triple.txt, and asserting into self, clauses that use an infix operator.

[114, 101, 118, 101, 114, 115, 101, 46, 108, 103, 116]

Simple object reading from a file, next.txt, and writing to another file, previous.txt, clauses that use infix operators.

[108, 111, 99, 97, 108, 46, 108, 103, 116]

Simple example of defining an operator local to a source file.

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

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:

%%table
double::double(I, J).

<!-- I = 1, J = 2 ; I = 2, J = 4 ; I = 3, J = 6 ; false. -->

Operators also affect inputting of terms, enabling this example to work:

triple::read_from_file.

<!-- true. -->

%%table
triple::triple(I, J).

<!-- I = 1, J = 3 ; I = 2, J = 6 ; I = 3, J = 9 ; false. -->

Local operators are used when reading terms (check the file previous.txt generated from the file next.txt by the object reverse by opening the files on a text editor):

reverse::reverse_file.

<!-- true. -->

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:

%%table
graph1::edge(N1, N2).

<!-- N1 = a, N2 = b ; N1 = a, N2 = c ; N1 = b, N2 = d ; N1 = c, N2 = d ; false. -->

%%table
graph1::path(a, d, Path).

<!-- Path = [a, b, d] ; Path = [a, c, d] ; false. -->

Confirm that the edge operator have not became global:

current_op(P, T, edge).

<!-- false. -->