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Re: What is going on!?!

  • To: mathgroup at
  • Subject: [mg104734] Re: [mg104688] What is going on!?!
  • From: "David Park" <djmpark at>
  • Date: Sun, 8 Nov 2009 06:46:57 -0500 (EST)
  • References: <23886295.1257594705714.JavaMail.root@n11>

I think it is generally a good technique to put multiple statements in one
cell, but you need to insert a line return (Enter) before the last x. That
is, the last x should be on a separate line - but in the same cell.

Because of the last ";" the For statement returned a Null, which would
normally suppress output from a line, but you multiplied it by x and that's
why you got 10 Null.

Generally, in Mathematica, it is better to use Procedural programming
statements. Something similar could be done with:

x = 0;
Do[x++, {10}]

x = 0; numbers = {x};
While[x < 10, x = x + 1; numbers = Join[numbers, {x}]]

David Park
djmpark at  

From: Joe Hays [mailto:joehays at] 

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

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