Power set: Difference between revisions

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→‎{{header|REXX}}: used a template for the output section, added/changed whitespace and comments, aligned some statements.
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m (→‎{{header|REXX}}: used a template for the output section, added/changed whitespace and comments, aligned some statements.)
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parse arg S /*allow the user specify optional set. */
if S='' then S= 'one two three four' /*Not specified? Then use the default.*/
@= '{}' /*start process with a null power set. */
N= words(S); do chunk=1 for N /*traipse through the items in the set.*/
@=@ combN(N, chunk) /*take N items, a CHUNK at a time. */
end /*chunk*/
w= length(2**N) /*the number of items in the power set.*/
do k=1 for words(@) /* [↓] show combinations, one per line*/
say right(k, w) word(@, k) /*display a single combination to term.*/
end /*k*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
combN: procedure expose S; parse arg x,y; base= x + 1; bbase=base-y; bbase= base - !.=0y
do p=1 for y; !.p=p; end /*p*/0
do up=d1 tofor y; !.u=p+1; if !.up==bbase+u then return .combU(u-1)p
$=$end '{'strip(L, "L", ',')"}"/*p*/
$=
do j=1; L=
do d=1 for y; L= L','word(S, !.d)
end /*d*/
 
$=$ '{'strip(L, "L", ',')"}"
!.y$=!.y+1$ '{'strip(L, "L", ',')"}"; if !.y==base then if !.combU(y-1)= !.y then+ leave1
if !.y==base then if .combU(y - 1) then leave
end /*j*/
return strip($) /*return with a partial powerset chunk.*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
.combU: procedure expose !. y bbase; parse arg d; if d==0 then return 1; p=!.d
p= !.d
do u=d to y; !.u=p+1; if !.u==bbase+u then return .combU(u-1)
pdo u=d to y; !.u= p + 1
if !.u==bbase+u then return .combU(u-1)
p= !.u
end /*u*/
return 0</lang>
'''{{out|output''' |text=&nbsp; when using the default input:}}
<pre>
1 {}