Double

Hi,
I have just scared. I expect that is here with some mathematical and physical constants, and get for a particular value for my double variable

"ExpTerm = 2.22184e-09"

out. The next step, I reckon (x is also a double)

Code:

 x = 1 - expTerm; 
court <<"1 - expTerm = "<<x <<endl;

However, the result gives me a "1 - 1 from expTerm ="!
In such an accuracy could, of course I completely forgot my account immediately. How can I increase the accuracy?

 

x = 1.0 - expTerm;

 

Hmm, this works for me no better:

Code:

# Include <iostream.h> 
# Include <stdlib.h> 

int main () 
( 
      double expTerm = 2.22184e-09; 
      court <<"expTerm = "<<expTerm <<endl; 
      expTerm expTerm = 1.0; 
      court <<"1.0 - expTerm = "<<expTerm <<endl; 
      system ("PAUSE"); 
      return 0; 
)  

is with me again
"1.0-expTerm = 1"

Is this due to my compiler, or at least to the number of Kleinhiet (exp ^ (-9))?

 

Actually, it should not be an issue, because according to the literature has a double
64 bit and can therefore theoretically represent a range of + -1.7 * 10 ^ (-308).
In <float.h> is also established that there are 52 double digits . This should actually be sufficient to calculate the difference specified correctly and also issue to ...

 

court <<setprecision (12);
are ne other 1

 

in the numeric_limits <T> there is in the double epsilon ^ -16 which is the value at which one-value = 1: O)