As I said, what you ask is non-standard, but you can achieve that with a trick:
#include <iostream>
#include <iomanip>
#include <cmath>
class Double {
public:
Double(double x): value(x) {}
const double value;
};
std::ostream & operator<< (std::ostream & stream, const Double & x) {
// So that the log does not scream
if (x.value == 0.) {
stream << 0.0;
return stream;
}
int exponent = floor(log10(std::abs(x.value)));
double base = x.value / pow(10, exponent);
// Transform here
base /= 10;
exponent += 1;
stream << base << 'E' << exponent; // Change the format as needed
return stream;
}
int main() {
// Use it like this
std::cout << std::setprecision(6) << std::fixed;
std::cout << Double(-2.203e-15) << std::endl;
return 0;
}
The Double
wrapper is needed because you cannot redefine <<
for double
.
I did not test that way of separating exponent
and base
against the odds of floating point, maybe you can come up with a better alternative, but you get the idea :)