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Re: fractional part of a number [message #7929]

Fri, 24 January 1997 00:00

thompson
Messages: 584
Registered: August 1991

Senior Member

davidf@dfanning.com (David Fanning) writes:

> Mirko Vukovic writes:

>>> How does one get the fractional part of a number? Could not find
>>> anything in the manual.

> Then Phil Williams answers:
>
>> Do you mean this:
>> IDL> n = 5.5
>> IDL> print, n mod floor(n)
>> 0.500000

> And Andy Loughe follows this with:

>> number = 5.89
>> frac_number = number - fix(number)

> BUT, and here is the important question: which is FASTER!

> No, no, I was just kidding. I do love these kinds of questions, though. :-)

Actually, neither of these approaches is completely robust, because of their
different behaviors for negative numbers,

IDL> n = -5.5
IDL> print, n mod floor(n)
-5.50000
IDL> print, n - fix(n)
-0.500000

I think the correct way to do it is to combine the two approaches,

IDL> print, n - floor(n)
0.500000

That is, if you agree with me that the integer part of -5.5 is -6, and the
fractional part is +0.5. :^)

Bill Thompson

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[Message index]

		Re: fractional part of a number By: thompson on Fri, 24 January 1997 00:00
		Re: fractional part of a number By: Andy Loughe on Thu, 23 January 1997 00:00
		Re: fractional part of a number By: Phil Williams on Thu, 23 January 1997 00:00
		Re: fractional part of a number By: davidf on Thu, 23 January 1997 00:00

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