a simple question

[zl2k]

hi,
In a function of a class, I have a unsigned long A (65535) and a
double B (0-1) and when I calculate a*b I should get a double 0-65535.
But, I get an unreasonable large value (e+9) if doing "cout<<A*B; ".
However, I get the correct value if doing "cout<<B*A; " or
"cout<<(double) A*B". Can someone explain what's wrong with the code?
If I take the piece out of the function and run it separately, both
A*B and B*A give the same correct result. Thanks for the comments.
zl2k

[Greg Herlihy]

Re: a simple question

On Apr 1, 10:24 pm, "zl2k" <kdsfin...@gmai l.comwrote:

hi,
In a function of a class, I have a unsigned long A (65535) and a
double B (0-1) and when I calculate a*b I should get a double 0-65535.
But, I get an unreasonable large value (e+9) if doing "cout<<A*B; ".
However, I get the correct value if doing "cout<<B*A; " or
"cout<<(double) A*B". Can someone explain what's wrong with the code?

What code?

Greg

[Jim Langston]

Re: a simple question

"zl2k" <kdsfinger@gmai l.comwrote in message
news:1175491442 .063918.111450@ o5g2000hsb.goog legroups.com...

hi,
In a function of a class, I have a unsigned long A (65535) and a
double B (0-1) and when I calculate a*b I should get a double 0-65535.
But, I get an unreasonable large value (e+9) if doing "cout<<A*B; ".
However, I get the correct value if doing "cout<<B*A; " or
"cout<<(double) A*B". Can someone explain what's wrong with the code?
If I take the piece out of the function and run it separately, both
A*B and B*A give the same correct result. Thanks for the comments.
zl2k

Following program outputs:
32767.5
32767.5
32767.5

which is not what you describe.

Please show the code you are doing.

#include <iostream>
#include <string>

int main()
{
unsigned long A = 65535;
double B = 0.5;

std::cout << A * B << "\n";
std::cout << B * A << "\n";
std::cout << double(A) * B << "\n";

std::string wait;
std::getline( std::cin, wait );

}