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Re: Printing numbers

  • To: mathgroup at
  • Subject: [mg54536] Re: [mg54483] Printing numbers
  • From: DrBob <drbob at>
  • Date: Tue, 22 Feb 2005 04:24:20 -0500 (EST)
  • References: <>
  • Reply-to: drbob at
  • Sender: owner-wri-mathgroup at

There's no reason to think ToString[123.456789] should have ten characters. In fact, it has seven:



That's because the default display for an approximate (machine precision) number is six decimal places. It could have been 1 or 100, after all. By the time the number is given to ToString, Mathematica has stored the number AS a number and forgotten what your InputForm was.

Similarly, ToString turns 1234567.89 into a two-line output taking up 22 characters:

"          6\n1.23457 10"

To control display of numbers, experiment with NumberForm, PaddedForm, AccountingForm, etc.

I doubt you'll be very happy with it.


On Mon, 21 Feb 2005 03:44:51 -0500 (EST), Steve Gray <stevebg at> wrote:

> 1. Can anyone tell me why these results are what they are? Neither answer is what I would expect,
> which is 10. The two strings are the same length.
> Print[StringLength[ToString[123.456789]], "   ",
>         StringLength[ToString[1234567.89]]];
> 7    22
> 2. Is there a simple, easily available or self-evident way to get numbers printed out such that the
> total  number of spaces occupied by the print before the decimal point is some fixed, user-specified
> amount, the number of spaces occupied after the decimal point is a different user-specified amount,
> and the number of spaces following the number is a third user-specified amount. The goal is to
> easily produce aligned columns of numerical printing, which would seem to be the most trivial task
> in neat number printing.
> 	For example if the function is called fprint, fprint[345.678,4,5,6] would print 4 spaces
> followed by 5 character positions to the left of the point (00345 or (2 spaces)" 345", specified by
> another argument), and 6 to its right. So fprint[345.678,4,5,6] would print (4 spaces)(2
> spaces)"345.678"(3 spaces), or if desired (4 spaces)(2 spaces)"345.678000"(no spaces), the total
> taking up 16 positions. Also fprint[-345.678,4,5,6] would print (4 spaces)(1 space)"-345.678"(3
> spaces), also taking 16 positions, with the decimal points aligned with the first example.
> 	Help is not that helpful, implying that I have to write one or find it somewhere. As I
> recall, C provides an easy way to do this by setting arguments to Print.
> 	Leads would be appreciated.
> Steve Gray

DrBob at

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