From: Kristof Bastiaensen <kristof@...>
Date: 2004-09-02T05:40:23+09:00
Subject: Re: invisible Infinity

On Thu, 02 Sep 2004 05:08:44 +0900, Mohammad Khan wrote:

> On Wed, 2004-09-01 at 15:55, Kristof Bastiaensen wrote:
>> On Thu, 02 Sep 2004 04:25:57 +0900, Mohammad Khan wrote:
>> 
>> > On Wed, 2004-09-01 at 15:22, Mohammad Khan wrote:
>> >> If you take a look in numeric.c
>> >> 
>> >> 
>> >> /*
>> >>  *  call-seq:
>> >>  *     flt.to_s    => string
>> >>  *
>> >>  *  Returns a string containing a representation of self. As well as
>> >>  a *
>> >>   fixed or exponential form of the number, the call may return *
>> >>  ``<code>NaN</code>'', ``<code>Infinity</code>'', and *
>> >>  ``<code>-Infinity</code>''.
>> >>  */
>> >>                                                                                                                                                              
>> >> static VALUE
>> >> flo_to_s(flt)
>> >>     VALUE flt;
>> >> {
>> >>     char buf[32];
>> >>     char *fmt = "%.15g";
>> >>     double value = RFLOAT(flt)->value;
>> >>     double avalue, d1, d2;
>> >>                                                                                                                                                              
>> >>     if (isinf(value))
>> >>         return rb_str_new2(value < 0 ? "-Infinity" : "Infinity");
>> >>     else if(isnan(value))
>> >>         return rb_str_new2("NaN");
>> >>                                                                                                                                                              
>> >>     avalue = fabs(value);
>> >>     if (avalue == 0.0) {
>> >>         fmt = "%.1f";
>> >>     }
>> >>     else if (avalue < 1.0e-3) {
>> >>         d1 = avalue;
>> >>         while (d1 < 1.0) d1 *= 10.0;
>> >>         d1 = modf(d1, &d2);
>> >>         if (d1 == 0) fmt = "%.1e";
>> >>     }
>> >>     else if (avalue >= 1.0e15) {
>> >>         d1 = avalue;
>> >>         while (d1 > 10.0) d1 /= 10.0;
>> >>         d1 = modf(d1, &d2);
>> >>         if (d1 == 0) fmt = "%.1e";
>> >>         else fmt = "%.16e";
>> >>     }
>> >>     else if ((d1 = modf(value, &d2)) == 0) {
>> >>         fmt = "%.1f";
>> >>     }
>> >>     sprintf(buf, fmt, value);
>> >>                                                                                                                                                              
>> >>     return rb_str_new2(buf);
>> >> }
>> >> }
>> >> Infinity and -Infinity is String and it is just a representation. It
>> >> is definitely, not a Constant.
>> >> 
>> >> I am wrong, correct me please.
>> > 
>> > I meant,
>> > If I am wrong, correct me please.
>> > 
>> > 
>> I am not sure if this is what you meant, but Infinity is not a string:
>> 
>> (10.0/0).class
>> => Float
>> 
>> (10.0/0).to_s.class
>> => String
> 
> irb(main):001:0> a = 10.0/0
> => Infinity
> irb(main):002:0> b = -20.0/0
> => -Infinity
> 
> I said, Infinity and -Infinity is just a String representation of Float,
> not a Constant.
> 

So it is not what you meant then :-)
It wasn't clear to me you where talking about irb output.
Sorry for the confusion.

> regards
> Mohammad
> 
> 
>> Regards,
>> KB