Javier Esteve wrote:
> I'm learning ruby, and I want to know if it is any way to know the
> biggest number to be represented with a specific type of number (Fixnum,
> Bignum, Float).

Float is a standard 64-bit IEEE floating point value. There are several 
constants on the Float class that can tell you whatever you need:

 jruby -e "p Float::constants"
["MAX", "MAX_10_EXP", "MANT_DIG", "RADIX", "DIG", "MIN", "ROUNDS", 
"MIN_EXP", "EPSILON", "MIN_10_EXP", "MAX_EXP"]

Fixnum has no such constants, but on most implementations (CRuby, JRuby, 
Rubinius at least) its max size is dependent on how large its basis 
representation is. I believe it can be either "32" or "64" bits on 
CRuby, where on JRuby it is always "64" bits:

 ruby -e "p (1 << (1.size * 8 - 1)) - 1"
2147483647

 ruby -e "p -(1 << (1.size * 8 - 1))"
-2147483648

 jruby -e "p (1 << (1.size * 8 - 1)) - 1"
9223372036854775807

 jruby -e "p -(1 << (1.size * 8 - 1))"
-9223372036854775808

The loss of one bit of precision on most impls is to emulate CRuby's 
implementation of Fixnum as a tagged pointer, where the top bit 
indicates whether an object pointer is a real pointer or a Fixnum value).

And Bignum has no min or max size, other than the maximum size of a 
byte[] on your system.

- Charlie