produce ( ..a pred: ( ..a -- ..b ? ) quot: ( ..b -- ..a obj ) -- ..b seq )
Factor handbook » The language » Collections » Sequence operations » Sequence combinators

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Vocabulary
sequences

Inputs

pred	a quotation with stack effect ( ..a -- ..b ? )
quot	a quotation with stack effect ( ..b -- ..a obj )

Outputs

seq	a sequence

Word description
Calls pred repeatedly. If the predicate yields f, stops, otherwise, calls quot to yield a value. Values are accumulated and returned in a sequence at the end.

Examples
The following example divides a number by two until we reach zero, and accumulates intermediate results:

USING: kernel math prettyprint sequences ; 1337 [ dup 0 > ] [ 2/ dup ] produce nip .
{ 668 334 167 83 41 20 10 5 2 1 0 }

The following example collects random numbers as long as they are greater than 1:

USING: kernel prettyprint random sequences ; [ 10 random dup 1 > ] [ ] produce nip .
{ 8 2 2 9 }

Definition

IN: sequences

: produce
    ( ..a pred: ( ..a -- ..b ? ) quot: ( ..b -- ..a obj ) -- ..b seq )
    { } produce-as ; inline