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MathGroup Archive 1997

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Re: [Help?] Integer/Decimal portion of a real number

  • To: mathgroup at smc.vnet.net
  • Subject: [mg8866] Re: [mg8847] [Help?] Integer/Decimal portion of a real number
  • From: Allan Hayes <hay at haystack.demon.co.uk>
  • Date: Tue, 30 Sep 1997 20:16:30 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

kammy shan leung <ksleung at students.uiuc.edu>
[mg8847] [Help?] Integer/Decimal portion of a real number
writes
> What I would like to do is break up a real number to
> its integer and decimal portion.
> For example:
>
>  4.12345 can be broken up to:
>
> integer_portion = 4
> decimal_portion = 12345

Kammy,

We have (slightly modifying your example)

inpt= IntegerPart[4.0012345]
	4
frpt=FractionalPart[4.0012345 ]
	0.0012345
		
But if you want to get 0012345 from the last output then one  
problem is to get the digits, which can be done) and another one is  
that 0012345 will be reduced to 12345 (which can be tackled by  
storing a list of digits or a string). For example

StringDrop[ToString[frpt],2]
	"0012345"

Strings can be converted by using the functions Characters and  
ToExpression.

If strings are acceptable then we can move into strings right at  
the beginning and get a function

infr[x_Real]:=
	(str = ToString[x];
		dp = StringPosition[str,"."][[1,1]];
	{StringTake[str,dp-1],StringDrop[str,dp]}
	)
	
Which gives
	
infr[4.0012345]
	{"4","0012345"}
	
	
Note: The function RealDigits stores the information about frpt  
that we want, but problems associated with approximatig inexact  
numbers show up:

RealDigits[frpt]
{{1,2,3,4,4,9,9,9,9,9,9,9,9,8,0,5},-2}


Allan Hayes
hay at haystack.demon.co.uk
http://www.haystack.demon.co.uk/training.html
voice:+44 (0)116 2714198
fax: +44 (0)116 2718642
Leicester,  UK




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