Re: help working with functions
- To: mathgroup at smc.vnet.net
- Subject: [mg59993] Re: help working with functions
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Sun, 28 Aug 2005 03:07:31 -0400 (EDT)
- Organization: The Open University, Milton Keynes, U.K.
- References: <dep7us$f1s$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
hawkmoon269 wrote:
> I have the following program written:
>
> Clear[a]; Clear[seq];
> seq = Array[a,10,0]; a[0]=0; a[1]=1;
> Do[a[k] = a[k-1] + a[k-2] + 0 4^(k-2), {k,2,10}];
> seq
>
> It works fine and correctly outputs
>
> {0, 1, 1, 2, 3, 5, 8, 13, 21, 34}
>
> My sense,though, is that this is inelegant newbie code and am
> interested in hearing alternative ways to program with the same output.
> Also, I would like to generalize this as a callable function with
> arguments i,j,n...something like:
>
> f[i_,j_,n_]:=
> Clear[a]; Clear[seq];
> seq = Array[a,n,0]; a[0]=0; a[1]=1
> Do[a[k] = a[k-1] + a[k-2] + i j^(k-2), {k,2,n}]
> seq
>
> So that
>
> f[0,4,10]
>
> would output
>
> {0, 1, 1, 2, 3, 5, 8, 13, 21, 34}
>
> I've tried variants of the foregoing, but can't get it to work
> correctly...
>
> Many thanks in advance for ideas and assistance etc.
>
> h
>
Use *Module* inside your function rather than *Clear*; pay attention
where to use commas and semi columns (they work just as the opposite as
in C). Finally, you really should investigate how to code according to
rule based and functional paradigms. Anyway, here is you function in
procedural style:
f[i_, j_, n_] := Module[{a, seq}, seq = Array[a, n, 0]; a[0] = 0; a[1] = 1;
Do[a[k] = a[k - 1] + a[k - 2] + i*j^(k - 2), {k, 2, n}]; seq]
In[2]:=
f[0, 4, 10]
Out[2]=
{0, 1, 1, 2, 3, 5, 8, 13, 21, 34}
Best regards,
/J.M.