From: Garance A Drosehn <drosihn@...>
Date: 2005-07-05T07:22:05+09:00
Subject: Ruby2c and large numbers

Checking out the writeup on Ruby2C at:

http://www.zenspider.com/~ryand/Ruby2C.pdf

there is one thing about the example on page 25 (of the pdf)
which concerns me a little bit.  The example has:

class MyTest
  def factorial(n)
    f = 1
    n.downto(2) { |x| f *= x }
    return f
  end
end

turn into:

static VALUE factorial(VALUE self,
                        VALUE _n) {
    long n = NUM2INT(_n);
    long f;
    long x;
    f = 1;
    x = n;
    while (x >= 2) {
        f = f * x;
        x = x - 1;
    };
    return INT2NUM(f);
} 

One nice thing about ruby is that the programmer does not have
to worry about supported-ranges for integer values.  Ruby just
switches from "fixnum" objects into "bignum" objects, without
any attention from the programmer.  It seems to me that the C
code that is listed above just assumes the multiplication of
'f * x' will not overflow.  Is that the case?

-- 
Garance Alistair Drosehn     =             drosihn@gmail.com