Re: 1.#R result from floating point arithmetic

From:

"Ben Voigt [C++ MVP]" <rbv@nospam.nospam>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 15 Nov 2007 09:31:03 -0600

Message-ID:

<uzxx7x5JIHA.1188@TK2MSFTNGP04.phx.gbl>

"HM" <henners8000@nospam.nospam> wrote in message
news:B9D77D75-4640-4243-BF3A-9BB0FAF153CC@microsoft.com...

I have traced the problem - the 1.#R value was the result of a square root
on
a very small number (so presumably an underflow).

Square root divides the exponent by two... so you wouldn't be able to
overflow or underflow. Or did I miss something critical?

"HM" wrote:

I'm using an ostringstream and then doing:

double doubleVal = calculateDouble();
stream << doubleVal;

Not all doubles get this value - so I imagine it is due to the
calculation,
further calcualtions using the number result in NAN values being returned
by
the double conversion.

thanks

"Charles Wang[MSFT]" wrote:

Hi,
To let us better understand your issue, could you please let us know
how
you converted the double to string? Any code snippet which can help us
reproduce your issue is better.
I performed a test with _ecvt and _ect_s, they all worked fine and did
not
reproduce your issue:
   int decimal, sign;
   char *buffer;
   int precision = 10;
   double source = 3.1415926535;

   buffer = _ecvt( source, precision, &decimal, &sign );
   printf( "source: %2.12f buffer: '%s' decimal: %d sign: %d\n",
           source, buffer, decimal, sign );

Look forward to your response and have a nice day!

Best regards,
Charles Wang
Microsoft Online Community Support
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