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includes

This example illustrates using the include/1 directive as both a file directive and an entity directive. It also illustrates how to use this directive to implement a simple persistency solution for an object database.

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

%versions

Start by loading the example:

logtalk_load(includes(loader)).

Test the use of the Logtalk include/1 directive as a file directive:

findall(Vowel, vowel(Vowel), Vowels).

<!-- Vowels = [a,e,i,o,u]. -->

Test the use of the Logtalk include/1 directive as an entity directive by getting a list of all capitals:

countries::capitals(Capitals).

<!-- Capitals = [berlim, lisbon, madrid, paris, varsovia]. -->

Test the use of the Logtalk include/1 directive as an entity directive by getting sets of countries with the same population:

setof(Countries, countries::same_population(Countries), Solutions).

<!-- Solutions = [[france, poland], [germany, spain], [portugal]]. -->

Show the initial counter values, which may depend on previous runs:

counters::counter(Counter, Value).

<!-- Counter = a, Value = ... ; Counter = b, Value = ... ; Counter = c, Value = ... ; false. -->

Increment one of the counters:

counters::inc_counter(b).

<!-- true. -->

Save the counters database:

counters::save_counters.

<!-- true. -->