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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: [mg69484] Re: question on changing 'type' of numbers
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 14 Sep 2006 06:54:54 -0400 (EDT)
  • References: <ee8h72$j38$1@smc.vnet.net>


Hi Nasser ,

I believe the answer is that 0.1 is an atom not an expression.

The Help says:"Head[expr] gives the head of expr"

Head[atom] seems to give the type of the atom.



Integer[0.1] is an expression, namely the function Integer with the 

argument 0.1. As there is no such function defined, the expression is 

not further evaluated.



Daniel



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?

> 

> 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

> 

> any idea?

> 

> ofcourse the question as to what should happen to the value of the variable 

> if for example I change the head of 0.5 from Real to Integer is another 

> matter. It seems in this case x remained 0.1 but only the head said Integer

> 

> x

> ----->Integer[0.1]

> 

> Now sure what the above really means :)

> 

> Nasser 

> 



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