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parametric

This folder contains some examples of parametric objects and categories. Object and category parameters are logical variables that are shared with all the entity predicates. This example illustrates accessing parameters using the parameter/1 and this/1 built-in methods. Parameters can also be accessed using parameter variables as illustrated by the parvars example.

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

%versions

Start by loading the example:

logtalk_load(parametric(loader)).

Some queries using the list parametric object:

%%table
[1, 2, 3]::member(X).

<!-- X = 1 ; X = 2 ; X = 3 ; false. -->

[1, 2, 3]::last(X).

<!-- X = 3. -->

[1, 2, 3]::nextto(2, Y).

<!-- Y = 3. -->

\+ []::member(_).

<!-- true. -->

Some queries using the time and date parametric objects:

date(Year, Month, Day)::today.

<!-- Year = 2000, Month = 8, Day = 15. -->

date(Year, _, _)::today, \+ date(Year, _, _)::leap_year.

<!-- Year = 2002. -->

time(Hours, Mins, Secs)::now.

<!-- Hours = 13, Mins = 52, Secs = 42. -->

rectangle(W, H, X, Y)::init, rectangle(W, H, X, Y)::move(3, 4, NR), NR::position(X2, Y2).

<!-- W = 2, H = 1, X = 0, Y = 0, NR = rectangle(2, 1, 3, 4), X2 = 3, Y2 = 4. -->

Some queries with parametric objects that define "setter" methods that return updated object identifiers:

person(sally, 20)::grow_older(NewId).

<!-- NewId = person(sally, 21). -->

employee(sally, 21, 1200)::give_raise(250, NewId).

<!-- NewId = employee(sally, 21, 1450). -->

Some queries with parametric categories:

speech(winter, wedding)::advice.

<!-- Clothes: [pants, sleeves, heavy] Speech: [happy, jokes]

true. -->