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Re: FindInstance with all positive numbers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg122488] Re: FindInstance with all positive numbers
  • From: Bob Hanlon <hanlonr357 at gmail.com>
  • Date: Sun, 30 Oct 2011 04:20:26 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201110291113.HAA05435@smc.vnet.net>

eqn = a + b + c + d == 15;

var = Variables[eqn[[1]]];

cond = And @@ Thread[var > 0];

FindInstance[eqn && cond, var]

{{a -> 15/8, b -> 15/2, c -> 15/4, d -> 15/8}}


Bob Hanlon


On Sat, Oct 29, 2011 at 7:13 AM, Arthur Grabovsky <shukrri at gmail.com> wrote:
> Hi,
>
> To ensure FindInstance[] returns all positive numbers I would do:
>
> FindInstance[a+b=5&&a>0&&b>0,{a,b}];
>
> However I need to do the same but without having to list all individual variables. The reason is that I will be iterating through lists with a large, variable number of elements so writing out a>0&&b>0 all the way until z>0 is impractical.
>
> Thanks.
>



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