       Re: need help

• To: mathgroup at smc.vnet.net
• Subject: [mg87330] Re: [mg87308] need help
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Tue, 8 Apr 2008 05:34:29 -0400 (EDT)

```ri = RandomInteger[{-100, 100}, 10]

{-19,-96,85,-6,-60,-21,40,78,-4,-82}

ri[[RandomInteger[Length[ri]]]]

78

sumf[x_Integer] := FindInstance[
a^2 + b^2 + c^2 + d^2 == x, {a, b, c, d}, Integers][]

sumf /@ {1, 4, 7}

{{a->0,b->0,c->1,d->0},{a->0,b->0,c->2,d->0},{a->1,b->1,c->2,d->1}}

Bob Hanlon

---- haitomi <tpnycity at yahoo.com> wrote:
> Hello All,
>
> I need help with two pure functions
>
> 1)  Li[Ranlist,x] that return a list of x element selected at random from Ranlist.  (Is there any way to gennerate random from Ranlist? For example I have RanList=Range[-100,100])
>
> 2) the function 4Sumf[x] is computing the sum of 4 squares of x. If I have x=1, this function will gennerate 1^2+0^2+0^2+0^2, if x=4 then 2^2+0^2+0^2+0^2, if x=7 then 2^2+1^2+1^2+1^2
>
> Is anyone out there have any ideas?
> Thanks All,
> Tomi
>

```

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