Converting floating point to fixed point

Question

In C++, what\'s the generic way to convert any floating point value (float) to fixed point (int, 16:16 or 24:8)?

EDIT: For clarification, fixed-poin

Answer 1

Here you go:

// A signed fixed-point 16:16 class
class FixedPoint_16_16
{
    short          intPart;
    unsigned short fracPart;

public:
    FixedPoint_16_16(double d)
    {
        *this = d; // calls operator=
    }

    FixedPoint_16_16& operator=(double d)
    {
        intPart = static_cast(d);
        fracPart = static_cast
                    (numeric_limits + 1.0)*d);
        return *this;
    }

    // Other operators can be defined here
};

EDIT: Here's a more general class based on anothercommon way to deal with fixed-point numbers (and which KPexEA pointed out):

template 
class fixed_point
{
    const static BaseType factor = 1 << FracDigits;

    BaseType data;

public:
    fixed_point(double d)
    {
        *this = d; // calls operator=
    }

    fixed_point& operator=(double d)
    {
        data = static_cast(d*factor);
        return *this;
    }

    BaseType raw_data() const
    {
        return data;
    }

    // Other operators can be defined here
};


fixed_point fp1;           // Will be signed 24:8 (if int is 32-bits)
fixed_point fp1; // Will be unsigned 16:16 (if int is 32-bits)