<interval> ( from to -- interval )

Vocabulary

math.intervals

Inputs

from	a { point included? } pair
to	a { point included? } pair

Outputs

interval

an interval

Word description

Creates a new interval. Usually it is more convenient to create intervals using one of the following words instead:

•	[a,b]
•	(a,b)
•	[a,b)
•	(a,b]
•	[a,inf]
•	(a,inf]
•	[-inf,b)
•	[-inf,b]

Definition

USING: combinators kernel math sequences ;

IN: math.intervals

: <interval> ( from to -- interval )
    {
        { [ 2dup [ first ] bi@ > ] [ 2drop empty-interval ] }
        {
            [ 2dup [ first ] bi@ number= ]
            [
                2dup [ second ] both?
                [ interval boa ] [ 2drop empty-interval ] if
            ]
        }
        {
            [ 2dup [ { -1/0. t } = ] [ { 1/0. t } = ] bi* and ]
            [ 2drop full-interval ]
        }
        [ interval boa ]
    } cond ;