head ( seq n -- headseq )
Factor handbook » The language » Collections » Sequence operations » Subsequences and slices

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Vocabulary
sequences

Inputs

seq	a sequence
n	a non-negative integer

Outputs

headseq

a new sequence

Word description
Outputs a new sequence consisting of the first n elements of the input sequence.

Examples

USING: sequences prettyprint ; { 1 2 3 4 5 6 7 } 2 head .
{ 1 2 }

When a sequence may not have enough elements:

USING: sequences prettyprint ; { 1 2 } 5 index-or-length head .
{ 1 2 }

Errors
Throws an error if the index is out of bounds.

See also
head*, head-slice, head-slice*

Definition

USING: sequences.private ;

IN: sequences

: head ( seq n -- headseq ) head-to-index subseq ;