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Re: Working in Modules

  • To: mathgroup at smc.vnet.net
  • Subject: [mg21086] Re: Working in Modules
  • From: "Stephen P Luttrell" <luttrell at signal.dra.hmg.gb>
  • Date: Sun, 12 Dec 1999 23:51:54 -0500 (EST)
  • Organization: Defence Evaluation and Research Agency
  • References: <7a2c0d$1ul@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

>This is my third attempt to post this question. No idea why it doesnt
>work. 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}
>                    ]


You need to change init to read as follows:

init[n_Integer]:=Module[
{s=Table[Random[Integer],{n n}],s1},
s1=s/.{0->-1};
Partition[s1,n]
]

In your version where you do

s/.{0->-1};
Partition[s,n]

the result of s/.{0->-1}; is not assigned back to s as you have assumed.

Stephen P Luttrell
Signal Processing and Imagery Department
DERA Malvern, St.Andrew's Road
Malvern, United Kingdom, WR14 3PS

+44 (0)1684 894046 (tel)
+44 (0)1684 894384 (fax)
luttrell at signal.dera.gov.uk (email)




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