Re: Help ! complex permutations

*To*: mathgroup at smc.vnet.net*Subject*: [mg7032] Re: Help ! complex permutations*From*: uyurtsever at dynatec.com (Ulvi Yurtsever)*Date*: Fri, 2 May 1997 21:30:56 -0400 (EDT)*Organization*: AT&T WorldNet Services*Sender*: owner-wri-mathgroup at wolfram.com

On 29 Apr 1997 21:40:11 -0400, Robert_P at pro-bel.co.uk (Robert Perkins) wrote: > >Robert_p > > E.g., for the case (your case, I think) when the ordering of elements IS significant, you might do: In[70]:= Flatten[Outer[f, {a,b}, {a,b}]]/.f->List Out[70]= {{a,a},{a,b},{b,a},{b,b}} In[71]:= Flatten[Outer[f, {a,b}, {a,b}, {a,b}]]/.f->List Out[71]={{a,a,a},{a,a,b},{a,b,a},{a,b,b},{b,a,a}, {b,a,b},{b,b,a},{b,b,b}} For the case where the ordering is NOT significant (in which case the total number of permutations is Binomial[n+|m|-1, |m|-1]), you might do: In[72]:= Union[Map[Sort,Flatten[Outer[f,{a,b},{a,b}]]/.f->List]] Out[72]={{a,a},{a,b},{b,b}} In[73]:= Union[Map[Sort,Flatten[ Outer[f,{a,b},{a,b}, {a,b}]]/.f->List]] Out[73]={{a,a,a},{a,a,b},{a,b,b},{b,b,b}} (Caution: these are quick & dirty implementations; ie with no attention paid to time or space efficiency.) best wishes Ulvi Yurtsever Senior Research Scientist Dynamics Technology, Inc. 21311 Hawthorne Blvd., Suite 300 Torrance, CA 90503-5610 (310) 543-5433, FAX: (310) 543-2117 email: uyurtsever at dynatec.com