1.109.2 Send methods

number ->minus: int|number

Subtract argument from value.

number ->plus: int|number

Add argument to value.

number ->times: int|number

Multiply value by argument.

number ->divide: int|number

Basic arithmetic operations. Note that arithmetic may also be performed by the function classes /, +, - and *. Numbers are useful as accumulators (see the various examples in this class). Functions are more convenient in expressions.

number ->equal: int|number|real

Succeeds if the argument represents the same value. Note that PCE type conversion converts real objects, number objects and text to ints and thus all the following succeed:

?- send(number(1), equal, 1).
?- send(number(1), equal, 1.0).
?- send(number(1), equal, number(1)).
?- send(number(1), equal, '1').

number ->larger_equal: int|number|real

Test if larger-or-equal than argument.

number ->less_equal: int|number|real

Test if less-or-equal than argument.

number ->not_equal: int|number|real

Test if not-equal to argument.

number ->smaller: int|number|real

Test if less than argument.

number ->larger: int|number|real

Compare the receiver to the argument by value. The receiver is tested to be {number->larger, number->smaller, ...} than the argument.

number ->minimum: int|number

Set value to largest of current and argument.

number ->maximum: int|number

Set number<-value to the {number->maximum, number->minimum} of the current number<-value and the argument. Useful in may computations. Suppose Chain is a chain holding string and we which to know the widest string given the font Font:

width_of_strings(Chain, Font, Width) :-
        new(W, number(0)),
        send(Chain, for_all,
                 message(W, maximum, ?(Font, width, @arg1))),
        get(W, value, Width),
        send(W, done).