Re: D equivalent of C++ reinterpret cast?

[Simen kjaeraas]

Bradley Mitchell <abstracta...@gmail.com> wrote:

    int xi = cast(int)cast(void*)x;

[...]

    x = cast(float)cast(void*)xi;

The simple solution (seeing as how x is an lvalue) is


    int xi = *cast(int*)&x;
[...]
    x = *cast(float*)ξ

Function version:

T reinterpret( T, U )( U value ) {
    return *cast( T* )&value;
}

There may be situations in which this will not work (though
I know of none, OTOH), and where using a union will:

T reinterpret( T, U )( U value ) {
    union Uni {
        U u;
        T t;
    }
    return Uni(value).t;
}

Of course, these are general solutions, and the easy solution
to your problem is to use a union directly:


float fastInvSqrt( float x ) {
    enum int INV_SQRT_N = 1597292357;
    enum float MULT = 1.000363245811462f;

    float mx = 0.5f * MULT * x;
    union Xu {
        float f;
        int i;
    }
    Xu xu = Xu(x);
    xu.i = INV_SQRT_N - (xu.i >> 1);
    return xu.f * (1.5f * MULT - mx * xu.f * xu.f);
}


--
Simen