From help-request at octave dot org Mon Dec 26 03:02:03 2005
Subject: Re: fractional remainder
From: David Bateman <David dot Bateman at motorola dot com>
To: kamaraju kusumanchi <raju dot mailinglists at gmail dot com>
Cc: help at octave dot org
Date: Mon, 26 Dec 2005 09:57:04 +0100

kamaraju kusumanchi wrote:

> blah BLABBER wrote:
>
>> Howdy folks,
>>
>> Question: I am a new Octave user and cannot figure out how to grab 
>> the remainder of a fraction. For example, if I take 3/4 = 0.75, I 
>> just want to grab the 75.
>>
>> Reason: I would like to check if the remainder is zero in order to 
>> determine if a number is odd or even. Any even number divided by 2 
>> will have a remainder of 0, odd numbers will not. I am using this for 
>> loop control.
>>
>> Problem: In Octave,  rem(3,4) gives 3. Obviously I do not understand 
>> this function. Can you please suggest the appropriate function to use.
>>
>> Thanks.
>
>
> Try the mod function.
>
>
> octave:1> mod(11,2)
> ans = 1
> octave:2> mod(10,2)
> ans = 0
> octave:3> mod(3,4)
> ans = 3
> octave:4> mod(7,4)
> ans = 3
>
> To read about a function you can use the help command. To read about 
> rem, type help rem at the octave prompt etc.,
>
> hth
> raju
>
If your goal is to see if an integer is odd/even try the bitand 
function. In C the typical way to check if an integer is odd if

 if (val & 1)
    /* This value is odd */
 else
    /* This value is even */

The equivalent in octave would be

if (bitand (val, 1))
   # This value is odd
else
   # This value is even
endif

This should probably be faster than mod.

D.

-- 
David Bateman                                David dot Bateman at motorola dot com
Motorola Labs - Paris                        +33 1 69 35 48 04 (Ph) 
Parc Les Algorithmes, Commune de St Aubin    +33 1 69 35 77 01 (Fax) 
91193 Gif-Sur-Yvette FRANCE

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