Re: Help ! complex permutations

*To*: mathgroup at smc.vnet.net*Subject*: [mg7054] Re: [mg6965] Help ! complex permutations*From*: Robert Pratt <rpratt at math.unc.edu>*Date*: Sat, 3 May 1997 22:04:46 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I believe the command to use in Mma 2.2.2 was Strings, which now appears to have been relegated to the Combinatorica standard package in Mma 3.0. Needs["DiscreteMath`Combinatorica`"] ?Strings "Strings[l, n] constructs all possible strings of length n from the elements of list l." Strings[{a,b},2] {{a,a},{a,b},{b,a},{b,b}} Strings[{a,b},3] {{a,a,a},{a,a,b},{a,b,a},{a,b,b},{b,a,a},{b,a,b},{b,b,a},{b,b,b}} Rob Pratt Department of Mathematics The University of North Carolina at Chapel Hill CB# 3250, 331 Phillips Hall Chapel Hill, NC 27599-3250 rpratt at math.unc.edu http://www.math.unc.edu/Grads/rpratt/ On Wed, 30 Apr 1997, Robert Perkins wrote: > I need to derive an algorithm, formula, which gives all the > possiblities, combinations, for any 'n' out of 'm' with the proviso > that any member of 'm' can be used multiple times and the selection > sequence is significant. > > Taking a trivial example if the input list 'm' is > > {a,b} > > the output list 'n' for any 2 gives > > {a,a},{a,b},{b,a},{b,b} > > For an output sequence of 3 from the same input list would give > > {a,a,a},{a,a,b},{a,b,b},{b,a,b},{b,b,a},{b,b,b} > > Life gets interesting for larger input sequences and ever larger > output selections. How about the input list containing 10 members and > the output list containing 20 members with the above rules applying? > > Can anyone point me in the right direction? A reference, clue or even > an algorithm would be very welcome ;) > > TIA > > Robert_p > > >