Re: Creating a recursive function which returns a sequence

*To*: mathgroup at smc.vnet.net*Subject*: [mg128498] Re: Creating a recursive function which returns a sequence*From*: Sseziwa Mukasa <mukasa at gmail.com>*Date*: Thu, 25 Oct 2012 01:42:54 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <20121024073207.54EC56881@smc.vnet.net>

Flatten does what you need. Also there's no need to use Return: (Debug) In[5]:= f[n_] := Module[{}, If[n < 0, {}, Flatten[{g[n], f[n - 1]}]]] (Debug) In[6]:= f[2] (Debug) Out[6]= {g[2], g[1], g[0]} Sequence makes no sense outside of a function, so you can just do Sequence@@f[n] when you want to insert the result as the argument of another function. Regards, Sseziwa On Oct 24, 2012, at 3:32 AM, Wei-Hsun Lin wrote: > Hello all, > > I would like to create a recursive function of which the returning > value is a sequence. For example, > > f[n_]:=Module[{}, > If[n<0,Return[Sequence[]]]; > Sequence[g[n],f[n-1]] > ] > > The above code doesn't work because the Sequence function was > evaluated before it's returned. > Could anyone please advise me as to what's is the usual way to achieve > this? Thank you very much! > > The result I want is > > f[2] > =Sequence[g[2],f[1]] > =Sequence[g[2],Sequence[g[1],f[0]]] > =Sequence[g[2],g[1],f[0]] > =Sequence[g[2],g[1],Sequence[g[0],f[-1]]] > =Sequence[g[2],g[1],g[0],f[-1]] > =Sequence[g[2],g[1],g[0],Sequence[]] > =Sequence[g[2],g[1],g[0]] > > Best regards, > Wei-Hsun >

**References**:**Creating a recursive function which returns a sequence***From:*Wei-Hsun Lin <wei.xun.lin@gmail.com>