'Pollux key generator program
Defint A-Z
Dim Shared Perm[30], Num[30], Max, N
Dim Shared Proxy$
Dim shared ncalls,depth,maxdepth
'Describe multiset: N=10 symbols
'four 0's, three 1's, three 2's
Num[0] = 4
Num[1] = 3
Num[2] = 3
Max=2
N = Num[0] + Num[1] + Num[2]

Proxy$ = ".-x"  'four dots
GenPerms(N)     'generate 4200 keys
Print "ncalls =";ncalls;" maxdepth=";maxdepth
Input x$

Proxy$ = "-.x"  'four dashes
GenPerms(N)     'generate 4200 keys
Print "ncalls =";ncalls;" maxdepth=";maxdepth
Input x$

Proxy$ = "x.-"  'four separator x's
GenPerms(N)     'generate 4200 keys
Print "ncalls =";ncalls;" maxdepth=";maxdepth
Input x$


'Convert permutation to symbols and
'print it.
SUB PrintPerm
  For I=N-1 To 0 Step -1
    Print Mid$(Proxy$,Perm[i]+1,1);
  Next I
  Print
End Sub

'Recursive permutation generator
'for multisets.
Sub GenPerms(n)
  depth=depth+1
  if depth>maxdepth then maxdepth=depth
  ncalls=ncalls+1
  If Num[0] = n Then
    PrintPerm
  Else
    For j=0 to Max
      If Num[j] > 0 Then
         Perm[n-1] = j
         Num[j] = Num[j]-1 
         GenPerms n-1
         Num[j] = Num[j]+1
         Perm[n-1] = 0
      End If 
    Next J
  End If
  depth=depth-1
End Sub