interval-union ( i1 i2 -- i3 )
Factor handbook » The language » Numbers » Intervals » Set-theoretic operations on intervals

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Vocabulary
math.intervals

Inputs

i1	an interval
i2	an interval

Outputs

i3	an interval

Word description
Outputs the smallest interval containing the set-theoretic union of i1 and i2 (the union itself may not be an interval).

Examples

USING: math.intervals prettyprint ; 1 5 [a,b] 10 15 [a,b] interval-union .
T{ interval { from { 1 t } } { to { 15 t } } }

USING: math.intervals prettyprint ; empty-interval empty-interval interval-union .
empty-interval

See also
interval-intersect

Definition

USING: arrays combinators kernel sequences ;

IN: math.intervals

: interval-union ( i1 i2 -- i3 )
    {
        { [ over empty-interval? ] [ nip ] }
        { [ dup empty-interval? ] [ drop ] }
        { [ over full-interval? ] [ drop ] }
        { [ dup full-interval? ] [ nip ] }
        [
            [ interval>points 2array ] bi@ append
            points>interval nan-not-ok
        ]
    } cond ;