From: Robert Klemme <shortcutter@...>
Date: 2006-06-04T18:32:54+09:00
Subject: Re: Ruby's Bignum

2006/6/4, David Balmain <dbalmain.ml@gmail.com>:
> On 6/4/06, David Balmain <dbalmain.ml@gmail.com> wrote:
> To cast an Integer to a 32-bit signed integer you can use pack/unpack
> like Park said, or you could do it like this;
>
> def to_32_bit_signed(val)
>     val |= -0x100000000 if (val & 0x80000000) > 0
>     val
> end

And if you need this in multiple places of the program then it's
probably worth while to create a new subclass of Integer that
restricts itself to 32 bit calculations

Int32 < Integer
  def initialize(x)
    @val = to_32(x)
  end
  def to_int ...
  def coerce(a,b) ...
  def hash() ...
  def eql?(x)
  def ==(x) ...
  def +(x) ...
  def -(x) ...
private
  def to_32(x) ...

end

It's a nice excercise to get used to operators and numercial coercion. :-)

Maybe we can even generalize that and put it into the standard lib -
something like a restricted integer that calculates with a max number
of bits.

Kind regards

robert

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