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Re: From PaddedForm to numbers?

  • To: mathgroup at
  • Subject: [mg80514] Re: From PaddedForm to numbers?
  • From: AES <siegman at>
  • Date: Fri, 24 Aug 2007 01:55:45 -0400 (EDT)
  • Organization: Stanford University
  • References: <faj6fp$9gt$> <fajn99$pb1$>

In article <fajn99$pb1$1 at>,
 David Bailey <dave at> wrote:

> PaddedForm is a wrapper - like MatrixForm, and many others. WRI have a 
> standard comment in relation to these - "PaddedForm acts as a ?wrapper?, 
> which affects printing, but not evaluation."
> The wording of this has always seemed to me unfortunate, because if you 
> leave wrapper round an object it looks OK, but can't be incorporated in 
>   a further calculation - in other words a wrapper certainly does affect 
> evaluation!

Amen.  Been caught by this repeatedly with TableForm -- especially if 
it's something like Table[ - - lengthy expression - -  ]//TableForm.

If the standard comment were changed to something like " . . .  affects 
printing, but not evaluation *of the expression inside the wrapper*", 
you'd at least.

By the way, if my test in 5.2 the other day was correct,

   x=7;  PaddedForm[x, 3, NumberForm->{"0",""} ]

produces 0007 -- which doesn't match my naive interpretation of "padding 
something out to three significant figures", especially since it 
expresses x = 7777 correctly as *four* significant figures.  (It doesn't 
make James Bond very happy either).

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