Non-continuous subsequences: Difference between revisions

=={{header|Quackery}}==

A sequence of n items has 2^n possible subsequences, including the empty sequence. These correspond to the numbers 0 to 2^n-1, where a one in the binary expansion of the number indicates inclusion in the subsequence of the corresponding item in the sequence. Non-continuous subsequences correspond to numbers where the binary expansion of the number has a one, followed by one or more zeroes, followed by a one.

<lang Quackery> [ dup 1 & dip [ 1 >> ] ] is 2/mod ( n --> n n )

[ 0 swap

[ dup 0 != while

2/mod iff

[ dip 1+ ] done

again ]

[ dup 0 != while

2/mod not iff

[ dip 1+ ] done

again ]

[ dup 0 != while

2/mod iff

[ dip 1+ ] done

again ]

drop 3 = ] is noncontinuous ( n --> b )

[ [] unrot

[ dup 0 != while

dip behead tuck

1 & iff

[ nested dip rot

join unrot ]

else drop

1 >> again ]

2drop ] is bitems ( [ n --> [ )

[ [] swap

dup size bit times

[ i^ noncontinuous if

[ dup i^ bitems

nested rot

join swap ] ]

drop ] is ncsubs ( [ --> [ )

' [ 1 2 3 4 ] ncsubs echo cr

$ "quackery" ncsubs 72 wrap$</lang>

{{out}}

<pre>[ [ 1 3 4 ] [ 1 2 4 ] [ 2 4 ] [ 1 4 ] [ 1 3 ] ]

qackery quckery uckery qckery quakery uakery qakery akery qukery ukery

qkery quacery uacery qacery acery qucery ucery qcery cery quaery uaery

qaery aery query uery qery quackry uackry qackry ackry quckry uckry

qckry ckry quakry uakry qakry akry qukry ukry qkry kry quacry uacry

qacry acry qucry ucry qcry cry quary uary qary ary qury ury qry quackey

uackey qackey ackey quckey uckey qckey ckey quakey uakey qakey akey

qukey ukey qkey key quacey uacey qacey acey qucey ucey qcey cey quaey

uaey qaey aey quey uey qey ey quacky uacky qacky acky qucky ucky qcky

cky quaky uaky qaky aky quky uky qky ky quacy uacy qacy acy qucy ucy qcy

cy quay uay qay ay quy uy qy qacker qucker ucker qcker quaker uaker

qaker aker quker uker qker quacer uacer qacer acer qucer ucer qcer cer

quaer uaer qaer aer quer uer qer quackr uackr qackr ackr quckr uckr qckr

ckr quakr uakr qakr akr qukr ukr qkr kr quacr uacr qacr acr qucr ucr qcr

cr quar uar qar ar qur ur qr qacke qucke ucke qcke quake uake qake ake

quke uke qke quace uace qace ace quce uce qce ce quae uae qae ae que ue

qe qack quck uck qck quak uak qak ak quk uk qk qac quc uc qc qa

</pre>