Double precision floating point disassembly/reassembly analyser

double.cpp

#include <cassert>
#include <cmath>
#include <iostream>
using namespace std;

void printbytes(double d) {
    unsigned long long int* pi = (unsigned long long int*) &d;
    unsigned long long int i = *pi;
    short int e = (i >> 52 & 0x7ff) - 1023;                  // Exponent
    unsigned long long int m = (i << 12 >> 12) + pow(2, 52); // Mantissa
    double absv = m * pow(2, e-52);                          // Absolute value
    double v = absv * (i >> 63 ? -1 : 1);                    // Set sign
    assert(v == d);

    cout << "Decimal:      "   << d        << endl;
    cout << "Hexadecimal:  0x" << hex << i << endl;
    cout << "Mantissa:     0x" << hex << m << endl;
    cout << "Exponent:     "   << dec << e << endl;
    cout << endl;
}

int main() {
  printbytes(2.0);
  printbytes(1.0);
  printbytes(3.1416);
  printbytes(-1);
  printbytes(-0.0008);
  printbytes(-8.39293849532e87);
}

I thought it would be fun to do this now that I'm learning C++.