Re: Building a list

• To: mathgroup at smc.vnet.net
• Subject: [mg47144] Re: Building a list
• From: drbob at bigfoot.com (Bobby R. Treat)
• Date: Sat, 27 Mar 2004 01:34:54 -0500 (EST)
• References: <c40sfi\$mp8\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```For instance...

f[a_,b_,c_List]:=Outer[f[a,b,#1,#2]&,c,c]
f[a,b,{x,y,z}]

{{f[a,b,x,x],f[a,b,x,y],f[a,b,x,z]},{f[a,b,y,x],f[a,b,y,y],f[a,b,y,z]},{
f[a,b,z,x],f[a,b,z,y],f[a,b,z,z]}}

Bobby

Mark Coleman <mark at markscoleman.com> wrote in message news:<c40sfi\$mp8\$1 at smc.vnet.net>...
> Greetings,
>
> I've got a relatively simple function f[a_,b_,c_,d_], where a and b are
> integers and c and d are lists (of reals), and f returns a real.
>
> I need to evaluate f on (potentially long) sets of lists and calculate
> a square "matrix" from the possible permutations of the elements in the
> lists. For instance
>
> If
>
> xlist={x1,x2,x3}
>
>
> I need to calculate
>
> {{f[a,b,x1,x1],f[a,b,x1,x2],f[a,b,x1,x3]},{f[a,b,x2,x1],f[a,b,x2,x2],f[a
> ,b,x2,x3]},{f[a,b,x3,x1],f[a,b,x3,x2],f[a,b,x3,x3]}}
>
> Note that f[a,b,c,d] does not equal f[a,b,d,c].
>
> My first reaction was that Outer[] might do this, but I cannot seem to
> get it to work. I'd appreciate any suggestions.
>
> Thanks,
>
> Mark

```

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