From: Mohammad Khan <mkhan@...>
Date: 2004-09-02T04:22:35+09:00
Subject: Re: invisible Infinity

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.

--
Mohammad


On Wed, 2004-09-01 at 15:05, Brian Schroeder wrote:
> On Wed, 01 Sep 2004 18:05:43 +0000, gabriele renzi wrote:
> 
> > Hi gurus and nubys,
> > 
> > I wonder, if you divide a Float by zero, you get Infinity:
> >  >> a=10.0/0
> > => Infinity
> > 
> > 
> > and you can even write code using Infinity like:
> >  >> 0.upto(a) do |x| p x end
> > 0
> > 1
> > 2
> > 3
> > ..
> > 
> > but if you try to access it directly you can't:
> >  >> Infinity
> > NameError: uninitialized constant Infinity
> >          from (irb):4
> > 
> > Should we be able to access Infinity directly? It seem a strange
> > unexplicable behaviour to me, that it exists but is not normally
> > accessible.
> 
> 
> I also was surprised, that Infinity is no predefined constant, as I used
> it in some algorithm where I needed to fill an Array with infinity, then
> iteratively reducing the values. In these cases infinity is much better
> than nil as a special value because it can be compared.
> 
> So I declared 1.0/0.0 as Infinity and ready. But I regard it as against
> the pols.
> 
> Greetings,
> 
> Brian
-- 
Mohammad Khan <mkhan@lextranet.com>
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