From: Joel VanderWerf <vjoel@...>
Date: 2007-04-30T14:59:32+09:00
Subject: Re: LONG2NUM vs LONG2FIX

Haoqi Haoqi wrote:
> what's the difference about "LONG2NUM and LONG2FIX" in ruby c api?

LONG2FIX will truncate into a Fixnum (a 31 bit signed integer). LONG2NUM 
  will convert to Bignum (arbitrary precision integer) if necessary.

> why not "return LONG2FIX after FIX2LONG"??
> thanks.

(-2**30).class  # => Fixnum
(2**30).class   # => Bignum
(-2**30).abs.class  # => Bignum

> ruby source file(numeric.c):
> /*
>  *  call-seq:
>  *     fix.abs -> aFixnum
>  *
>  *  Returns the absolute value of <i>fix</i>.
>  *
>  *     -12345.abs   #=> 12345
>  *     12345.abs    #=> 12345
>  *
>  */
> 
> static VALUE
> fix_abs(fix)
>     VALUE fix;
> {
>     long i = FIX2LONG(fix);
> 
>     if (i < 0) i = -i;
> 
>     return LONG2NUM(i);
> }
> 

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407