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Null Return for a Module

  • To: mathgroup at smc.vnet.net
  • Subject: [mg88666] Null Return for a Module
  • From: Dave the Funkatron <dave.rudolf at usask.ca>
  • Date: Mon, 12 May 2008 04:45:17 -0400 (EDT)

Hi all,

I'm getting strange output and am trying to track down what might be
causing it. I have the following code in my .nb file:

(* begin code *)

Test[ ] := Module[ {i, thesum},
  	thesum = 0;
  	For[ i = 1, i <= 3, i++,
    		thesum = thesum + i
    	]
   	 Return[ thesum  ]
  ]

Test[ ]

(* end code *)


The output I would expect would be simply

  6

But, I get

  Null Return[6]

Alternatively, if I change the last line of the Test function to be

   	thesum

instead of

   	Return[ thesum ]

I get

  6 Null

as the output. If I remove the for loop, I get expected behavior,
i.e.,


Test[ ] := Module[ {i, thesum},
  	thesum = 1 + 2 + 3;
  	(*
  	For[ i = 1, i <= 3, i++,
  		thesum = thesum + i
  	]
  	*)
  	 Return[ thesum  ]
  ]

yields the output

  6

as one might expect. I'm not sure what this all means, or what it is
complaining about. I have other for-loops that are apparently working
properly. So, can anyone give me an idea what might be going wrong
here?

Thanks.

Dave




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