Unexplained warning creating vectors

Below is a printout of from my terminal when I create two vectors开发者_如何学C of ones. Does anyone know the reason why the second call to ones() issues a warning, while the first does not?

>> p1

p1 =

    0.7000

>> p2

p2 =

    0.3000

>> whos p1
  Name      Size            Bytes  Class     Attributes

  p1        1x1                 8  double              

>> whos p2
  Name      Size            Bytes  Class     Attributes

  p2        1x1                 8  double              

>> N

N =

   100

>> T1 = ones(N*p1,1);
>> T2 = ones(N*p2,1);
Warning: Size vector should be a row vector with integer elements. 

Yes, you might think that 100*.3 would be an integer, but it is not. This is because 0.3 is not stored as exactly 0.3 in the IEEE numeric representation used. Most such decimal numbers are not represented exactly. Remember that numbers are stored in a binary form. The true decimal representation of what is stored when you enter 0.3 into matlab is:

0.299999999999999988897769753748434595763683319091796875

It is close to 0.3, but not exactly so.

http://www.mit.edu/~pwb/cssm/matlab-faq_toc.html

http://download.oracle.com/docs/cd/E19957-01/806-3568/ncg_goldberg.html

Sometimes a result will turn out to be an exact integer.