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Re: mathematica newbie trouble

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99309] Re: mathematica newbie trouble
  • From: Bob F <deepyogurt at gmail.com>
  • Date: Sat, 2 May 2009 06:00:36 -0400 (EDT)
  • References: <gtegon$1vu$1@smc.vnet.net>

On May 1, 3:52 am, Guapo <yangsh... at gmail.com> wrote:
> i wrote the following mathematica code:
>
> s := (a + b + c)/2;
> k[a_, b_, c_] := Sqrt[s (s - a) (s - b) (s - c)];
> k[3, 4, 5]
> k[5, 9, 12]
>
> when run it, i can't get the write answer. but i change setDelayed(:=)
> to set(=), everything works ok
>
> s = (a + b + c)/2;
> k[a_, b_, c_] = Sqrt[s (s - a) (s - b) (s - c)];
> k[3, 4, 5]
> k[5, 9, 12]
>
> i did a google search for the difference of set and setDelayed,
> however, i still can't understand it for the upper described problem,
> could anyone explain it? great thanks.

You could change this to something like:

k[a_, b_, c_] := {
  s = (a + b + c)/2;
  Sqrt[s (s - a) (s - b) (s - c)]
  }
k[3, 4, 5]
k[5, 9, 12]

-Bob


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