2guard ( ..a x y quot: ( ..a x y -- ..b ? ) -- ..b x/f y/f )
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Vocabulary
kernel

Inputs

x	an object
y	an object
quot	a quotation

Outputs

x/f	an object
y/f	an object

Word description
Calls quot on x and y and either keeps x and y or replaces them with f.

Examples
True case:

USING: kernel math prettyprint ; 3 4 [ + odd? ] 2guard [ . ] bi@
3 4

False case:

USING: kernel math prettyprint ; 3 4 [ + even? ] 2guard [ . ] bi@
f f

See also
1check, 1guard, 2check, 3check, 3guard

Definition

IN: kernel

: 2guard
    ( ..a x y quot: ( ..a x y -- ..b ? ) -- ..b x/f y/f )
    2check [ 2drop f f ] unless ; inline