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MathGroup Archive 2006

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Re: question on changing 'type' of numbers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg69508] Re: [mg69473] question on changing 'type' of numbers
  • From: Sseziwa Mukasa <mukasa at jeol.com>
  • Date: Thu, 14 Sep 2006 06:56:27 -0400 (EDT)
  • References: <200609130803.EAA18407@smc.vnet.net>

On Sep 13, 2006, at 4:03 AM, Nasser Abbasi wrote:

> I think of a the Head of expression as its 'type'.
>
> One is supposed to be able to use Apply[f,expr] to change head of  
> expression
> to f.
>
> But Why can't I use this to change the head of a Real number to  
> Integer?

Because Reals and Integers are atoms, you can't change the head of an  
atom.

> In[122]:=
> Remove["Global`*"]
> x = 0.1
> Head[x]
>            -------------->Real
> Apply[Integer,x]
> Head[x]
>         ------------------->Real. I was expecting Intger
> x = Integer[x]
> Head[x]
>       ----------------> Now it says Integer

It says Integer, but it's not an integer in the same sense that 9 is  
an integer.  Integer[x] is an expression with the head Integer, which  
is a symbol, and body x, 9 is an expression with the head Integer and  
no body, you can take Integer[x] apart eg.

In[189]:=
Integer[x]ã??1ã??
Out[189]=
x

You cannot take 9 apart because it is an atom.


> Now sure what the above really means :)

Hope this helps,

Ssezi


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