Data Update

Task/Combinations/REXX/combinations-2.rexx

@@ -0,0 +1,47 @@
+/*REXX program displays combination sets for X things taken Y at a time.         */
+Parse Arg things size characters
+If things='?' Then Do
+  Say 'rexx combi2 things size characters'
+  Say ' defaults:  5      3    123456789...'
+  Say 'example rexx combi2 , , xyzuvw'
+  Say 'size<0 shows only the number of possible combinations'
+  Exit
+  End
+If things==''|things=="," Then things=5  /* No things specified? Then use default*/
+If size==''  |size==","   Then size=3    /* No size   specified? Then use default*/
+Numeric Digits 20
+show=sign(size)
+size=abs(size)
+If things<size Then
+  Call exit 'Not enough things ('things') for size ('size').'    Say '----------' things 'things taken' size 'at a time:'
+n=2**things-1
+nc=0
+Do u=1 to n
+  nc=nc+combinations(u)
+  End
+Say '------------' nc 'combinations.'
+Exit
+combinations: Procedure Expose things size characters show
+  Parse Arg u
+  nc=0
+  bu=x2b(d2x(u))
+  bu1=space(translate(bu,' ',0),0)
+  If length(bu1)=size Then Do
+    ub=reverse(bu)
+    res=''
+    Do i=1 To things
+      If characters<>'' then
+        c=substr(characters,i,1)
+      Else
+        c=i
+      If substr(ub,i,1)=1 Then res=res c
+      End
+    If show=1 then
+      Say res
+    Return 1
+    End
+  Else
+    Return 0
+exit:
+  Say '*****error*****' arg(1)
+  Exit 13