Prev: Solid C++ by example
Next: best way to disambiguate an overloaded function.
From: Rick.Regan on 28 Jun 2010 06:14
{ Please use a proper style of quoting. With the style used here,
it is difficult for the readers to find out which article your
reply is made to and which context it is referring to. The canonical
style goes like this:

<example>
previous author wrote:
> the previous content

what you add to it

> the previous content

what you add to it
</example>

Note that the previous content is marked by a quoting mark (">")
and your content follows after the quoted content. -mod }

When I convert "0.0003" and "3.e-4" in VC++ they are the same value:
0x1.3a92a30553261p-12.


George Neuner wrote:

Yes, I am aware of this. However, conversion of "0.0003" and "3.
28-Jun-10

Yes, I am aware of this. However, conversion of "0.0003" and "3.e-4"
should produce the same bits. In VC++, the two conversions produce
different results. This (IMO and that of many others) is wrong.

George


Previous Posts In This Thread:


Submitted via EggHeadCafe - Software Developer Portal of Choice
Composite UI Pattern And Enterprise Settings
http://www.eggheadcafe.com/tutorials/aspnet/ff14a008-2af9-4f9d-a09d-1af670466a80/aspnet-gridview-select-row-and-display-item-detail.aspx

--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]

From: George Neuner on 29 Jun 2010 16:54
On Mon, 28 Jun 2010 15:14:45 CST, Rick.Regan(a)giganews.com wrote:


>When I convert "0.0003" and "3.e-4" in VC++ they are the same value:

Which version are you using and how are you doing it?

VC2002,03,05 and 08 all fail to produce equivalent values when using
stream input, but scanf() produces equivalent values in all of them.
It doesn't matter whether the text is parsed from a file or from a
string.



int main( void )
{
double v1, v2, v3, v4;

std::cin >> v1 >> v2;
std::cout << std::endl << v1
<< std::string((v1 != v2) ? " != " : " == ")
<< v2
<< std::endl;
scanf( "%lf %lf", &v3, &v4 );
std::cout << std::endl << v3
<< std::string((v3 != v4) ? " != " : " == ")
<< v4
<< std::endl;
return 0;
}

with input: 3e-4
0.0003
3e-4
0.0003

produces output:
0.0003 != 0.0003
0.0003 == 0.0003

With the understanding that VC's debugger doesn't necessarily show all
the digits of a double, the values are:
v1 = 0.00029999999999999997
v2 = 0.00030000000000000003
v3 = 0.00029999999999999997
v4 = 0.00029999999999999997


>0x1.3a92a30553261p-12.

What the heck is that?

George

--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
[ comp.lang.c++.moderated. First time posters: Do this! ]

 | 
Pages: 1
Prev: Solid C++ by example
Next: best way to disambiguate an overloaded function.