I ran the following simple code in C++ and got unexpected results:
float f = 139.4;
cout << f;
Output:
139.399994;
if( f == 139.4)
cout << "Expected result";
else
cout << "Unexpected result";
Output:
Unexpected reult
I ran the following equivalent code in VB but got the correct results.
Dim f As Single
f = 139.4
Print f
If f = 139.4 Then
Print "Expected result"
Else
Print "Unexpected result"
End If
Doesn't this look bad on C++'s resume? 13 3616
On Mon, 12 May 2008 08:09:47 -0700, bintom wrote:
I ran the following simple code in C++ and got unexpected results:
float f = 139.4;
cout << f;
Output:
139.399994;
if( f == 139.4)
cout << "Expected result";
else
cout << "Unexpected result";
Output:
Unexpected reult
[...]
Doesn't this look bad on C++'s resume?
No, it looks bad on *your* resume ;-) http://www.parashift.com/c++-faq-lit...html#faq-29.16
--
Lionel B
On May 12, 8:23*pm, Lionel B <m...@privacy.n etwrote:
On Mon, 12 May 2008 08:09:47 -0700, bintom wrote:
I ran the following simple code in C++ and got unexpected results:
float f = 139.4;
cout << f;
Output:
139.399994;
if( f == 139.4)
* cout << "Expected result";
else
* cout << "Unexpected result";
Output:
Unexpected reult
[...]
Doesn't this look bad on C++'s resume?
No, it looks bad on *your* resume ;-)
http://www.parashift.com/c++-faq-lit...html#faq-29.16
--
Lionel B- Hide quoted text -
- Show quoted text -
Thanks Lionel for directing me to the link, but my question remains
unanswered. Should it be a computer science issue as it says on the
site, VB should've produced a similar (inaccurate) result. I'm just
trying to defend my resume.
On Mon, 12 May 2008 08:59:36 -0700, bintom wrote:
On May 12, 8:23Â*pm, Lionel B <m...@privacy.n etwrote:
>On Mon, 12 May 2008 08:09:47 -0700, bintom wrote:
I ran the following simple code in C++ and got unexpected results:
float f = 139.4;
cout << f;
Output:
139.399994;
if( f == 139.4)
Â* cout << "Expected result";
else
Â* cout << "Unexpected result";
Output:
Unexpected reult
[...]
Doesn't this look bad on C++'s resume?
No, it looks bad on *your* resume ;-)
http://www.parashift.com/c++-faq-lit...html#faq-29.16
Thanks Lionel for directing me to the link, but my question remains
unanswered. Should it be a computer science issue as it says on the
site, VB should've produced a similar (inaccurate) result. I'm just
trying to defend my resume.
As it happens, on my system your C++ code produces the "correct" result.
But that's irrelevant - as the FAQ says: floating point is an
approximation. This is inescapable. If you're interested in pursuing the
issue further, have a look at the classic article: "What Every Computer
Scientist Should Know About Floating-Point Arithmetic" http://docs.sun.com/source/806-3568/ncg_goldberg.html
--
Lionel B
bintom wrote:
>[..] http://www.parashift.com/c++-faq-lit...html#faq-29.16
-- Lionel B- Hide quoted text -
- Show quoted text -
Thanks Lionel for directing me to the link, but my question remains
unanswered. Should it be a computer science issue as it says on the
site, VB should've produced a similar (inaccurate) result. I'm just
trying to defend my resume.
Defending one's resume is a waste of time. You need to learn what
you don't know and _update_ your resume. If you like how VB handles
things, you should stay with VB.
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask
On 2008-05-12 17:59, bintom wrote:
On May 12, 8:23 pm, Lionel B <m...@privacy.n etwrote:
>On Mon, 12 May 2008 08:09:47 -0700, bintom wrote:
I ran the following simple code in C++ and got unexpected results:
float f = 139.4;
cout << f;
Output:
139.399994;
if( f == 139.4)
cout << "Expected result";
else
cout << "Unexpected result";
Output:
Unexpected reult
[...]
Doesn't this look bad on C++'s resume?
No, it looks bad on *your* resume ;-)
http://www.parashift.com/c++-faq-lit...html#faq-29.16
Please do not quote signatures.
Thanks Lionel for directing me to the link, but my question remains
unanswered. Should it be a computer science issue as it says on the
site, VB should've produced a similar (inaccurate) result. I'm just
trying to defend my resume.
You are comparing apples to pears, f is a float while 13.4 is a double
(an advice, always turn up the warning levels and fix as many of them as
you can), try this code and see what it does:
#include <iostream>
int main()
{
float f = 139.4f;
std::cout << f << "\n";
if( f == 139.4f)
std::cout << "Expected result\n";
else
std::cout << "Unexpected result\n";
}
--
Erik Wikström
On Mon, 12 May 2008 16:42:20 +0000, Erik Wikström wrote:
On 2008-05-12 17:59, bintom wrote:
>On May 12, 8:23 pm, Lionel B <m...@privacy.n etwrote:
>>On Mon, 12 May 2008 08:09:47 -0700, bintom wrote: I ran the following simple code in C++ and got unexpected results:
float f = 139.4; cout << f;
Output: 139.399994;
if( f == 139.4) cout << "Expected result"; else cout << "Unexpected result";
Output: Unexpected reult
[...]
Doesn't this look bad on C++'s resume?
No, it looks bad on *your* resume ;-)
http://www.parashift.com/c++-faq-lit...html#faq-29.16
Please do not quote signatures.
>Thanks Lionel for directing me to the link, but my question remains unanswered. Should it be a computer science issue as it says on the site, VB should've produced a similar (inaccurate) result. I'm just trying to defend my resume.
You are comparing apples to pears, f is a float while 13.4 is a double
(an advice, always turn up the warning levels and fix as many of them as
you can), try this code and see what it does:
#include <iostream>
int main()
{
float f = 139.4f;
std::cout << f << "\n";
if( f == 139.4f)
std::cout << "Expected result\n";
else
std::cout << "Unexpected result\n";
}
On my system (compiler GCC 4.1.2) with
float f = 139.4;
and compiled with:
g++ -std=c++98 -pedantic -Wall -Wextra
I get no warnings and the output is 'Expected result'. Should the
compiler warn if there's an implicit conversion? Or only if it results in
loss of precision?
--
Lionel B
On May 12, 3:08*pm, Lionel B <m...@privacy.n etwrote:
>
On my system (compiler GCC 4.1.2) with
* float f = 139.4;
and compiled with:
* g++ -std=c++98 -pedantic -Wall -Wextra
I get no warnings and the output is 'Expected result'. Should the
compiler warn if there's an implicit conversion? Or only if it results in
loss of precision?
The g++ compiler can issue a warning if you want one:
g++ -Wshorten-64-to-32
Greg
On Mon, 12 May 2008 16:02:54 -0700, Greg Herlihy wrote:
On May 12, 3:08Â*pm, Lionel B <m...@privacy.n etwrote:
>> On my system (compiler GCC 4.1.2) with
Â* float f = 139.4;
and compiled with:
Â* g++ -std=c++98 -pedantic -Wall -Wextra
I get no warnings and the output is 'Expected result'. Should the compiler warn if there's an implicit conversion? Or only if it results in loss of precision?
The g++ compiler can issue a warning if you want one:
g++ -Wshorten-64-to-32
cc1plus: error: unrecognized command line option "-Wshorten-64-to-32"
GCC 4.3.0 on x86_64
Anyway, that doesn't sound like a floating-point warning...
--
Lionel B
On Tue, 13 May 2008 08:55:23 +0000, Lionel B wrote:
On Mon, 12 May 2008 16:02:54 -0700, Greg Herlihy wrote:
>On May 12, 3:08Â*pm, Lionel B <m...@privacy.n etwrote:
>>> On my system (compiler GCC 4.1.2) with
Â* float f = 139.4;
and compiled with:
Â* g++ -std=c++98 -pedantic -Wall -Wextra
I get no warnings and the output is 'Expected result'. Should the compiler warn if there's an implicit conversion? Or only if it results in loss of precision?
The g++ compiler can issue a warning if you want one:
g++ -Wshorten-64-to-32
cc1plus: error: unrecognized command line option "-Wshorten-64-to-32"
GCC 4.3.0 on x86_64
Anyway, that doesn't sound like a floating-point warning...
This does it: -Wconversion. With
float f = 139.4;
warning: conversion to ‘float’ alters ‘double’ constant value
--
Lionel B This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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