Power set: Difference between revisions
added PL/I translated from REXX
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Walterpachl (talk | contribs) (added PL/I translated from REXX) |
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(mapcar '((X) (cons (car Lst) X)) L)
L ) ) ) )</lang>
=={{header|PL/I}}==
<lang pli>*process source attributes xref or(!);
/*--------------------------------------------------------------------
* 06.01.2014 Walter Pachl translated from REXX
*-------------------------------------------------------------------*/
powerset: Proc Options(main);
Dcl (hbound,index,left,substr) Builtin;
Dcl sysprint Print;
Dcl s(4) Char(5) Var Init('one','two','three','four');
Dcl ps Char(1000) Var;
Dcl (n,chunk,p) Bin Fixed(31);
n=hbound(s); /* number of items in the list. */
ps='{} '; /* start with a null power set. */
Do chunk=1 To n; /* loop through the ... . */
ps=ps!!combn(chunk); /* a CHUNK at a time. */
End;
Do While(ps>'');
p=index(ps,' ');
Put Edit(left(ps,p-1))(Skip,a);
ps=substr(ps,p+1);
End;
combn: Proc(y) Returns(Char(1000) Var);
/*--------------------------------------------------------------------
* returns the list of subsets with y elements of set s
*-------------------------------------------------------------------*/
Dcl (y,base,bbase,ym,p,j,d,u) Bin Fixed(31);
Dcl (z,l) Char(1000) Var Init('');
Dcl a(20) Bin Fixed(31) Init((20)0);
Dcl i Bin Fixed(31);
base=hbound(s)+1;
bbase=base-y;
ym=y-1;
Do p=1 To y;
a(p)=p;
End;
Do j=1 By 1;
l='';
Do d=1 To y;
u=a(d);
l=l!!','!!s(u);
End;
z=z!!'{'!!substr(l,2)!!'} ';
a(y)=a(y)+1;
If a(y)=base Then
If ym=hbound(s) Then
Leave;
End;
/* Put Edit('combn',y,z)(Skip,a,f(2),x(1),a); */
Return(z);
End;
End;</lang>
'''output'''
<pre>{}
{one}
{two}
{three}
{four}
{one,two}
{one,three}
{one,four}
{two,three}
{two,four}
{three,four}
{one,two,three}
{one,two,four}
{one,three,four}
{two,three,four}
{one,two,three,four}</pre>
=={{header|Prolog}}==
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