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Re: What is going on!?!

• To: mathgroup at smc.vnet.net
• Subject: [mg104727] Re: [mg104688] What is going on!?!
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Sun, 8 Nov 2009 06:44:49 -0500 (EST)
• Reply-to: hanlonr at cox.net

The output of the For is Null (from documentation on For: "Unless an explicit Return is used, the value returned by For is Null."). When multiplied by x (i.e., 10) gives 10*Null. Put the semi-colon after the right bracket.

x = 0;
For[i = 1, i <= 10, i++, x = x + 1]; x

10


Bob Hanlon

---- Joe Hays <joehays at vt.edu> wrote: 

=============
Can anyone tell me why the output is not a simple "10" instead of "10 Null"?

In[3]:= x = 0;
For[i = 1, i <= 10, i++,
  x = x + 1;
  ] x

Out[4]= 10 Null