Vocabulary
sequences

Inputs and outputs

seq	a sequence
elt	an object
newseq	a sequence

Word description
Outputs a new sequence obtained by adding elt at the beginning of seq.

Errors
Throws an error if the type of elt is not permitted in sequences of the same class as seq1.

Examples

USING: prettyprint sequences ; { 1 2 3 } 0 prefix .
{ 0 1 2 3 }

See also
push, suffix

Definition

USING: kernel math sequences.private ;

IN: sequences

: prefix ( seq elt -- newseq )
over [ over length 1 + ] dip
[ [ 0 swap set-nth-unsafe ] keep [ 1 swap copy ] keep ]
new-like ;