Re: Re:QuestionUsenet
- To: mathgroup at smc.vnet.net
- Subject: [mg77950] Re: [mg77917] Re:QuestionUsenet
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Wed, 20 Jun 2007 05:36:33 -0400 (EDT)
- References: <200706191059.GAA08415@smc.vnet.net> <C119CE43-CC22-4A0F-812D-672E9181A52D@mimuw.edu.pl>
On 20 Jun 2007, at 10:19, Andrzej Kozlowski wrote:
> *This message was transferred with a trial version of CommuniGate
> (tm) Pro*
>
> On 19 Jun 2007, at 19:59, JanPax wrote:
>
>>
>> Hi,
>> what is the easiest way to generate (in Mathematica) ALL terms
>> given some
>> function symbols and their arities
>> and variables x,y, like e.g. f unary, g binary, up to depth N?
>> x,y, f(x),f(y),g(x,f(x)),g(x,f(y))....
>> Or even better, to generate *next* term at one step, so that all
>> terms up
>> to depth N will be reached once.
>>
>> Thank you, JP
>>
>>
>
> Assuming that you mean what I think you mean, here is one way (up
> to level 2 - it's clear how to continue beyond that).
I should have written "up to depth three" .
Andrzej Kozlowski
>
> SetAttributes[F, {Flat, OneIdentity, Orderless}]
>
> FF0[l_List] := ReplaceList[l, {___, x_ /; Length[{x}] == 1, ___} :>
> G[x]]
> FF1[l_List] := ReplaceList[(F[##1] & ) @@ l, F[x_, y_] :> F[x, G[y]]]
> FF2[l_List] := ReplaceList[(F[##1] & ) @@ l, F[x_, y_] :> F[G[x], G
> [y]]]
>
> p = Tuples[{a, b}, 2];
>
> Reverse[Union[Flatten[({FF0[#1], FF1[##1], FF2[##1]} & ) /@ p]]] /.
> {F -> g, G -> f}
>
> {f[b], f[a], g[f[b], f[b]], g[f[a], f[b]], g[f[a], f[a]], g[b, f
> [b]], g[b, f[a]],
> g[a, f[b]], g[a, f[a]]}
>
> q=Tuples[{a,b,c},2];
>
> Reverse[Union[Flatten[({FF0[#1], FF1[##1], FF2[##1]} & ) /@ q]]] /.
> {F -> g, G -> f}
>
> {f[c], f[b], f[a], g[f[c], f[c]], g[f[b], f[c]], g[f[b], f[b]], g[f
> [a], f[c]],
> g[f[a], f[b]], g[f[a], f[a]], g[c, f[c]], g[c, f[b]], g[c, f[a]],
> g[b, f[c]],
> g[b, f[b]], g[b, f[a]], g[a, f[c]], g[a, f[b]], g[a, f[a]]}
>
> etc.
>
>
> Andrzej Kozlowski
- References:
- Re:QuestionUsenet
- From: JanPax <pax0@seznam.cz>
- Re:QuestionUsenet