C++

Forum

 
How to use '&' and '>>' on a double number

tnjgraham (87)
Hey,
I am working on a project where I need to retrive a double number and store 8 bits of the number in one field and the other 16 bits in another field. the code below gives me an error.

1
2
3
 
  lata= lat>>8;
  latb = (lat & 0xff);


The error states that & and >> are illegal for double. With this in mind, can I use these on a double. If not what can I do to achieve what I am trying to do? Any help will be greatly appreciated.

MiiNiPaa (8886)
floating point numbers have intricate inner structure, so there is no sense in shift and bitwise and operators for them.

If you can tell me what do you want I might be able to help you

To illustrate:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
 
#include<iostream>
#include<cassert>
#include<iomanip>

int main() {
    double d = 3.1415;
    assert(sizeof(d) == sizeof(unsigned long long));
    /*Make sure that our conversions are correct*/
    unsigned long long l = *reinterpret_cast<unsigned long long*>(&d);
    std::cout << std::fixed << std::setprecision(20) 
              << (*reinterpret_cast<double*>(&l) ) << std::endl;
    /*Shifting value as if it was integer */
    l = *reinterpret_cast<unsigned long long*>(&d) >> 1;
    std::cout << std::fixed << std::setprecision(20)
              << (*reinterpret_cast<double*>(&l) ) << std::endl;
}
 
Result:
3.14150000000000018119
0.00000000000000000000

And that what happens if I use -3.1415:
-3.14150000000000018119
34468122235899929731268127252972631307719631954602084229973957663296898131825128231025492077425653771839651515076174809397381002673182873761219166865457152.00000000000000000000
Last edited on
Topic archived. No new replies allowed.