EKG sequence convergence: Difference between revisions

</pre>

=={{header|Factor}}==

{{works with|Factor|0.99 2019-10-06}}

<lang factor>USING: combinators.short-circuit formatting fry io kernel lists

lists.lazy math math.statistics prettyprint sequences

sequences.generalizations ;

: ekg? ( n seq -- ? )

{ [ member? not ] [ last gcd nip 1 > ] } 2&& ;

: (ekg) ( seq -- seq' )

2 lfrom over [ ekg? ] curry lfilter car suffix! ;

: ekg ( n limit -- seq )

[ 1 ] [ V{ } 2sequence ] [ 2 - [ (ekg) ] times ] tri* ;

: show-ekgs ( seq n -- )

'[ dup _ ekg "EKG(%d) = %[%d, %]\n" printf ] each ;

: converge-at ( n m max -- o )

tuck [ ekg [ cum-sum ] [ rest-slice ] bi ] 2bi@

[ swapd [ = ] 2bi@ and ] 4 nfind 4drop dup [ 2 + ] when ;

{ 2 5 7 9 10 } 20 show-ekgs nl

"EKG(5) and EKG(7) converge at term " write

5 7 100 converge-at .</lang>

{{out}}

<pre>

EKG(2) = { 1, 2, 4, 6, 3, 9, 12, 8, 10, 5, 15, 18, 14, 7, 21, 24, 16, 20, 22, 11 }

EKG(5) = { 1, 5, 10, 2, 4, 6, 3, 9, 12, 8, 14, 7, 21, 15, 18, 16, 20, 22, 11, 33 }

EKG(7) = { 1, 7, 14, 2, 4, 6, 3, 9, 12, 8, 10, 5, 15, 18, 16, 20, 22, 11, 33, 21 }

EKG(9) = { 1, 9, 3, 6, 2, 4, 8, 10, 5, 15, 12, 14, 7, 21, 18, 16, 20, 22, 11, 33 }

EKG(10) = { 1, 10, 2, 4, 6, 3, 9, 12, 8, 14, 7, 21, 15, 5, 20, 16, 18, 22, 11, 33 }

EKG(5) and EKG(7) converge at term 21