Jari Williamsson wrote:
> Which is the best approach to avoid division rounding errors when 
> performing integer division with a Fixnum? Is there any built-in method 
> for this?
> 
> Best regards,
> 
> Jari Williamsson
> 
> 
> 

I'm not sure what you're trying to accomplish here. Fixnums by 
definition are integers. When you divide an integer by another integer, 
you can get either a quotient, a remainder (the "modulo" operation), or 
a list of both the quotient and remainder. For example, in irb:

irb(main):001:0> fixnum1 = 5
=> 5
irb(main):002:0> fixnum2 = 7
=> 7
irb(main):003:0> fixnum1/fixnum2
=> 0
irb(main):004:0> fixnum1%fixnum2
=> 5
irb(main):005:0> fixnum1.divmod fixnum2
=> [0, 5]

There are two other options. You can convert the Fixnums to Floats and 
get their quotient as another Float:

irb(main):006:0> fixnum1.to_f/fixnum2.to_f
=> 0.714285714285714

Or, you can enter the world of Rational numbers and represent the 
quotient of two integers as a Rational, like this:

irb(main):007:0> require 'mathn'
=> true
irb(main):008:0> fixnum1/fixnum2
=> 5/7


The tradeoffs between these last two options are (in most languages) 
performance versus accuracy. The floating point version will usually be 
faster, and the amount of memory required is fixed. But its accuracy is 
limited to about 15 decimal places in most machines.

The rational version will be slower, and the numbers involved can take 
up arbitrarily large amounts of memory as the computation progresses. 
But it is "exact", in the sense that if the result you're seeking is a 
rational number, that's what you'll get. If the result isn't a rational 
number, you'll get a rational number that's close to it.