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MathGroup Archive 1999

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Re: Dont Understand

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15936] Re: [mg15857] Dont Understand
  • From: "Tomas Garza" <tgarza at mail.internet.com.mx>
  • Date: Wed, 17 Feb 1999 23:34:03 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

Don McKenzie Paul wrote:

>I'm not an expert in Mathematica and would appreciate comments on why
>init1 returns a list with all zeros replaced by -1, but init does not.
>Its probably very simple but its confused me.

>Don

>init[n_Integer]:=Module[
                    {s=Table[Random[Integer],{n n}]},
                    s/.{0->-1};
                    Partition[s,n]
                    ]

>init1[n_Integer]:=Module[
                    {s=Table[Random[Integer],{n n}]},
                    s/.{0->-1}
                    ]

Don,
In init you use a transformation rule on s, but never assign the result to
something. Hence the Partition is applied to the original s. Try something
like

init[n_Integer]:=Module[
                    {s=Table[Random[Integer],{n n}]},
                    z=s/.{0->-1};
                    Partition[z,n]
                    ]

However, in init1 you perform the transformation without a semicolon at the
end, hence the result is simply displayed on the screen -- you can do
nothing with it until you assign it to a symbol.

Good luck,

Tomas Garza
Mexico City



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