unless-empty ( ... seq quot: ( ... seq -- ... ) -- ... )
Factor handbook » The language » Collections » Sequence operations » Control flow with sequences

Prev:

when-empty ( ... seq quot: ( ... -- ... obj ) -- ... seq/obj )

Vocabulary
sequences

Inputs

seq	a sequence
quot	the second quotation of an if-empty

Outputs
None

Word description
Makes an implicit check if the sequence is empty. An empty sequence is dropped. Otherwise, the quot is called on the sequence.

Examples
This word is equivalent to if-empty with an empty first quotation:

USING: sequences prettyprint ; { 4 5 6 } [ ] [ sum . ] if-empty
15

USING: sequences prettyprint ; { 4 5 6 } [ sum . ] unless-empty
15

Definition

USING: kernel ;

IN: sequences

: unless-empty ( ... seq quot: ( ... seq -- ... ) -- ... )
    [ ] swap if-empty ; inline