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MathGroup Archive 2007

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Re: Weird Print Result

  • To: mathgroup at
  • Subject: [mg74167] Re: [mg74122] Weird Print Result
  • From: Bob Hanlon <hanlonr at>
  • Date: Tue, 13 Mar 2007 03:40:31 -0500 (EST)
  • Reply-to: hanlonr at

Put a semi-colon after the Print statement. 

The output of--vice the action (print) of--a Print statement is a Null. You mapped Print onto a Plus with four terms and the result is the Plus of four Nulls (4 Null). Similarly,

Print /@ (A*B)




Times of two Nulls is Null squared. Again, a semi-colon would have suppress the output of--but not the action of--the Print.

Bob Hanlon

---- Bruce Colletti <vze269bv at> wrote: 
> Re Mathematica 5.2 under WinXP.
> The code below creates the correct output, except for a strange concluding "4 Null."
> What does this weird last line of output mean (list length?), why does it print, and how can it be suppressed?
> Thankx.
> Bruce
> n = 2;
> T = Array[p, {n, n}];
> X0 = Array[x, {n}];
> X = (Expand /@ (X0.MatrixPower[T, 2]));
> Print /@ X[[1]]

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