lengthen ( n seq -- )
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Vocabulary
sequences

Inputs

n	a non-negative integer
seq	a resizable sequence

Outputs
None

Generic word contract
Ensures the sequence has a length of at least n elements. This word differs from set-length in two respects:

•	This word does not shrink the sequence if n is less than its length.
•	The word doubles the underlying storage of seq, whereas set-length is permitted to set it to equal n. This ensures that repeated calls to this word with constant increments of n do not result in a quadratic amount of copying, so that for example push-all can run efficiently when used in a loop.

Examples

USING: kernel prettyprint sequences ; 6 V{ 1 1 1 1 } [ lengthen ] keep .
V{ 1 1 1 1 0 0 }

Showing how the underlying storage grows:

USING: accessors kernel prettyprint sequences ; 6 V{ 1 1 1 1 } [ lengthen ] keep underlying>> .
{ 1 1 1 1 0 0 0 0 0 0 0 0 0 0 }

When n is less than the length of seq:

USING: kernel prettyprint sequences ; 2 V{ 1 2 3 4 5 6 7 8 } [ lengthen ] keep .
V{ 1 2 3 4 5 6 7 8 }

Definition

IN: sequences

GENERIC: lengthen ( n seq -- )

Methods

USING: accessors growable kernel math sequences ;

M: growable lengthen
    2dup length > [
        2dup capacity > [ over new-size over expand ] when
        2dup length<<
    ] when 2drop ; inline


USING: kernel math sequences ;

M: sequence lengthen
    [ length > ] 2check [ set-length ] [ 2drop ] if ; inline


USING: accessors kernel sequences xml.data ;

M: tag lengthen [ children>> ] call \ lengthen execute ;


USING: accessors kernel sequences xml.data ;

M: xml-chunk lengthen [ seq>> ] call \ lengthen execute ;


USING: accessors kernel sequences xml.data ;

M: xml lengthen [ body>> ] call \ lengthen execute ;