From: Greg Hauptmann <greg.hauptmann.ruby@...>
Date: 2008-11-08T16:44:53+09:00
Subject: Re: what's easiest way to compare a Float & BigDecimal (i.e. like a equals mechanism)

that works - but my 6.5 number doesn't work - does the following also
not work for you?

>> a = BigDecimal.new('6.5')
=> #<BigDecimal:238875c,'0.65E1',8(8)>
>> b = 6.5
=> 6.5
>> a == b
=> false
>> a.class
=> BigDecimal
>> b.class
=> Float
>>

On Sat, Nov 8, 2008 at 5:03 PM, Michael Morin <uzimonkey@gmail.com> wrote:
> Greg Hauptmann wrote:
>>
>> Hi,
>>
>> what's easiest way to compare a Float & BigDecimal (i.e. like a equals
>> mechanism)?  It seems that "==" does NOT work as they are different
>> types.  Is there a way to do a comparison without having to convert
>> types?
>>
>> ?> a
>> => #<BigDecimal:2395e98,'0.65E1',8(8)>
>>>>
>>>> x
>>
>> => 6.5
>>>>
>>>> a == x
>>
>> => false      #<<== DIDN'T WORK
>>
>> tks
>>
>
>
> It works fine for me.  If I do something like this:
>
> f = 0.1
> b = BigDecimal.new('0.1')
> puts 'yes' if f == b
>
> It will return true.  I've always stayed clear of the equality operator with
> floating point numbers.  Floating point cannot represent all numbers
> exactly, so comparing it with something like a BigDecimal (which can
> represent all numbers exactly) might be problematic.
>
>