C / C++ / MFC

// Common.h
#pragma once
#ifndef COMMON_H
#define COMMON_H

typedef unsigned __int8  __uint8 ;
typedef unsigned __int16 __uint16;
typedef unsigned __int32 __uint32;
typedef unsigned __int64 __uint64;

// Template structures used to get information about IEEE floating-point formats
template<size_t bytes> struct __float {
public:
    // Mantissa size, in bits
    static const __uint8  MantissaSize;
    // Significand size, in bits
    static const __uint8  SignificandSize;
    // Exponent size, in bits
    static const __uint8  ExponentSize;
    // The maximum representable exponent (reserved for inf and NaN)
    static const __uint16 ExponentMax;
    // The exponent bias
    static const __uint16 ExponentBias;
    // An integer with only the bit left of the mantissa set
    static const __int64 SignificandBit;
    // An integer with all bits included in the mantissa set
    static const __int64 MantissaMask;
    static const __int64 SignificandMask;
    // An integer with all bits included in the exponent set
    static const __int64 ExponentMask;
};
    
// Defines the constants used by the __float structure
template<> const __uint8 __float< 2>::MantissaSize =  10;
template<> const __uint8 __float< 4>::MantissaSize =  23;
template<> const __uint8 __float< 8>::MantissaSize =  52;
    
// Compute the constants for the __float structure
template<size_t bytes>
const __uint8  __float<bytes>::SignificandSize = __float<bytes>::MantissaSize + 1;
template<size_t bytes>
const __uint8  __float<bytes>::ExponentSize    = (bytes << 3) - __float<bytes>::SignificandSize;
template<size_t bytes>
const __uint16 __float<bytes>::ExponentMax     = (1 << __float<bytes>::ExponentSize) - 1;
template<size_t bytes>
const __uint16 __float<bytes>::ExponentBias    = __float<bytes>::ExponentMax >> 1;
template<size_t bytes>
const __int64 __float<bytes>::SignificandBit  =
    static_cast<__int64>(1) << __float<bytes>::MantissaSize;
template<size_t bytes>
const __int64 __float<bytes>::MantissaMask    =
    __float<bytes>::SignificandBit - 1;
template<size_t bytes>
const __int64 __float<bytes>::SignificandMask =
    __float<bytes>::SignificandBit | __float<bytes>::MantissaMask;
template<size_t bytes>
const __int64 __float<bytes>::ExponentMask    =
    static_cast<__int64>(__float<bytes>::ExponentMax) <<
    __float<bytes>::MantissaSize;
    
#endif

// Main.cpp
#include <iostream>
#include "Common.h"

using namespace std;

double getOnePointFive() {
    __uint64 rval(0);
    rval = (static_cast<__uint64>(__float<8>::ExponentBias) << __float<8>::MantissaSize) |
           (1ULL << (__float<8>::MantissaSize - 1));
    return *reinterpret_cast<double*>(&rval);
}
    
int main(int argc, const char* argv[]) {
    cout << getOnePointFive() << endl;
    cout << __float<8>::ExponentBias << endl;
    cin.get();
    return 0;
}