Hofstadter Figure-Figure sequences: Difference between revisions

=={{header|Factor}}==

<lang factor>: next ( s r -- news newr )

2dup [ last ] bi@ + suffix

dup [

[ dup last 1 + dup ] dip member? [ 1 + ] when suffix

] dip ;</lang>

Tests:

<lang factor>( scratchpad ) { 2 } { 1 } 1000 [ next ] times ! Generate the first 1000 values of S and R

--- Data stack:

{ 2 4 5 6 8 9 10 11 13 14 15 16 17 19 20 ~986 more~ }

{ 1 3 7 12 18 26 35 45 56 69 83 98 114 131 150 ~986 more~ }

( scratchpad ) dup 10 head .

{ 1 3 7 12 18 26 35 45 56 69 }

--- Data stack:

{ 2 4 5 6 8 9 10 11 13 14 15 16 17 19 20 ~986 more~ }

{ 1 3 7 12 18 26 35 45 56 69 83 98 114 131 150 ~986 more~ }

( scratchpad ) [ 960 head ] [ 40 head ] bi* append ! Combine the first 960 terms of S and the first 40 of R

--- Data stack:

{ 2 4 5 6 8 9 10 11 13 14 15 16 17 19 20 ~985 more~ }

( scratchpad ) 1000 iota [ 1 + ] map [ dupd swap member? ] map t [ and ] reduce . clear

t</lang>