next ( s r -- news newr )

Vocabulary

rosetta-code.hofstadter-ffs

Inputs

s	an object
r	an object

Outputs

news	an object
newr	an object

Definition

USING: kernel math sequences ;

IN: rosetta-code.hofstadter-ffs

: next ( s r -- news newr )
    2dup [ last ] bi@ + suffix dup
    [ [ dup last 1 + dup ] dip member? [ 1 + ] when suffix ] dip
    ;