exchange-subseq ( len pos1 pos2 seq -- )

Vocabulary

sequences.extras

Inputs

len	a non-negative integer
pos1	a non-negative integer
pos2	a non-negative integer
seq	a mutable sequence

Outputs

None

Word description

Exchanges the contents of subsequences [pos1, pos1+len) and [pos2, pos2+len) in seq. Overlapping ranges are allowed. If either of the ranges exceeds the seq length, throws an error before any modifications take place. If len = 1, the behavior is equivalent to exchange.

Examples

Non-overlapping ranges:

USING: kernel sequences.extras prettyprint ; 2 0 3 "01_34_" [ exchange-subseq ] keep .
"34_01_"

Overlapping ranges:

USING: kernel sequences.extras prettyprint ; 3 0 2 "abcdef" [ exchange-subseq ] keep .
"cdebaf"

Side effects

Modifies seq

See also

exchange

Definition

USING: kernel math math.order sequences sequences.private ;

IN: sequences.extras

: exchange-subseq ( len pos1 pos2 seq -- )
    [ [ assert-non-negative ] tri@ 3dup max + 1 - ] dip
    bounds-check nip [ [ 2dup ] ] dip
    [ exchange-unsafe [ 1 - ] [ 1 + ] [ 1 + ] tri* ] curry
    compose [ pick 0 > ] swap while 3drop ;