vec4.h from Boson at Krugle

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#ifndef GFXVEC4_INCLUDED // -*- C++ -*-
#define GFXVEC4_INCLUDED
#if !defined(__GNUC__)
#  pragma once
#endif

/************************************************************************

  4D Vector class
  
  $Id: vec4.h 7779 2006-10-04 20:42:56Z abmann $

 ************************************************************************/

#include "vec3.h"

template<class T>
class TVec4 {
private:
    T elt[4];

public:
    // Standard constructors
    //
    TVec4(T s=0) { *this = s; }
    TVec4(T x, T y, T z, T w) { elt[0]=x; elt[1]=y; elt[2]=z; elt[3]=w; }

    // Copy constructors & assignment operators
    template<class U> TVec4(const TVec4<U>& v) { *this = v; }
    template<class U> TVec4(const TVec3<U>& v,T w)
    	{ elt[0]=v[0];  elt[1]=v[1];  elt[2]=v[2];  elt[3]=w; }
    template<class U> TVec4(const U v[4])
    	{ elt[0]=v[0]; elt[1]=v[1]; elt[2]=v[2]; elt[3]=v[3]; }
    template<class U> TVec4& operator=(const TVec4<U>& v)
	{ elt[0]=v[0];  elt[1]=v[1];  elt[2]=v[2]; elt[3]=v[3]; return *this; }
    TVec4& operator=(T s) { elt[0]=elt[1]=elt[2]=elt[3]=s; return *this; }


    // Descriptive interface
    //
    typedef T value_type;
    static int dim() { return 4; }


    // Access methods
    //
    operator       T*()       { return elt; }
    operator const T*() const { return elt; }

#ifndef HAVE_CASTING_LIMITS
    T& operator[](int i)       { return elt[i]; }
    T  operator[](int i) const { return elt[i]; }
    operator const T*()       { return elt; }
#endif

    // Assignment and in-place arithmetic methods
    //
    inline TVec4& operator+=(const TVec4& v);
    inline TVec4& operator-=(const TVec4& v);
    inline TVec4& operator*=(T s);
    inline TVec4& operator/=(T s);
};

////////////////////////////////////////////////////////////////////////
//
// Method definitions
//

template<class T> inline TVec4<T>& TVec4<T>::operator+=(const TVec4<T>& v)
    { elt[0]+=v[0];  elt[1]+=v[1];  elt[2]+=v[2];  elt[3]+=v[3]; return *this;}

template<class T> inline TVec4<T>& TVec4<T>::operator-=(const TVec4<T>& v)
    { elt[0]-=v[0];  elt[1]-=v[1];  elt[2]-=v[2];  elt[3]-=v[3]; return *this;}

template<class T> inline TVec4<T>& TVec4<T>::operator*=(T s)
    { elt[0] *= s;   elt[1] *= s;   elt[2] *= s;  elt[3] *= s; return *this; }

template<class T> inline TVec4<T>& TVec4<T>::operator/=(T s)
    { elt[0] /= s;   elt[1] /= s;   elt[2] /= s;  elt[3] /= s; return *this; }


////////////////////////////////////////////////////////////////////////
//
// Operator definitions
//

template<class T>
inline TVec4<T> operator+(const TVec4<T> &u, const TVec4<T> &v)
	{ return TVec4<T>(u[0]+v[0], u[1]+v[1], u[2]+v[2], u[3]+v[3]); }

template<class T>
inline TVec4<T> operator-(const TVec4<T> &u, const TVec4<T>& v)
	{ return TVec4<T>(u[0]-v[0], u[1]-v[1], u[2]-v[2], u[3]-v[3]); }

template<class T> inline TVec4<T> operator-(const TVec4<T> &u)
	{ return TVec4<T>(-u[0], -u[1], -u[2], -u[3]); }

#if defined _MSC_VER && _MSC_VER>=1200
// Normally, we use the <class T, class N> construct below to allow the scalar
// argument to be different than the template type.  This, for example, allows
// the user to write things like v/2.  Unfortunately, Microsoft VC6.0 (aka
// v1200) gets confused by this.  We used to include explicit versions for the
// case of int's, but this was causing silent (and incorrect) coercion of
// floats to ints.
//
  template<class T> inline TVec4<T> operator*(T s, const TVec4<T> &v)
	{ return TVec4<T>(v[0]*s, v[1]*s, v[2]*s, v[3]*s); }
  template<class T> inline TVec4<T> operator*(const TVec4<T> &v, T s)
	{ return s*v; }

  template<class T> inline TVec4<T> operator/(const TVec4<T> &v, T s)
	{ return TVec4<T>(v[0]/s, v[1]/s, v[2]/s, v[3]/s); }
#else
  template<class T, class N> inline TVec4<T> operator*(N s, const TVec4<T> &v)
	{ return TVec4<T>(v[0]*s, v[1]*s, v[2]*s, v[3]*s); }
  template<class T, class N> inline TVec4<T> operator*(const TVec4<T> &v, N s)
	{ return s*v; }

  template<class T, class N> inline TVec4<T> operator/(const TVec4<T> &v, N s)
	{ return TVec4<T>(v[0]/s, v[1]/s, v[2]/s, v[3]/s); }
#endif

template<class T> inline T operator*(const TVec4<T> &u, const TVec4<T> &v)
	{ return u[0]*v[0] + u[1]*v[1] + u[2]*v[2] + u[3]*v[3]; }

template<class T>
inline std::ostream &operator<<(std::ostream &out, const TVec4<T>& v)
	{ return out <<v[0] <<" " <<v[1] <<" " <<v[2] <<" " <<v[3]; }

template<class T>
inline std::istream &operator>>(std::istream &in, TVec4<T>& v)
	{ return in >> v[0] >> v[1] >> v[2] >> v[3]; }

////////////////////////////////////////////////////////////////////////
//
// Misc. function definitions
//

template<class T>
inline TVec4<T> cross(const TVec4<T>& a, const TVec4<T>& b, const TVec4<T>& c)
{
    // Code adapted from VecLib4d.c in Graphics Gems V

    T d1 = (b[2] * c[3]) - (b[3] * c[2]);
    T d2 = (b[1] * c[3]) - (b[3] * c[1]);
    T d3 = (b[1] * c[2]) - (b[2] * c[1]);
    T d4 = (b[0] * c[3]) - (b[3] * c[0]);
    T d5 = (b[0] * c[2]) - (b[2] * c[0]);
    T d6 = (b[0] * c[1]) - (b[1] * c[0]);

    return TVec4<T>(- a[1] * d1 + a[2] * d2 - a[3] * d3,
		      a[0] * d1 - a[2] * d4 + a[3] * d5,
		    - a[0] * d2 + a[1] * d4 - a[3] * d6,
		      a[0] * d3 - a[1] * d5 + a[2] * d6);
}

template<class T> inline T norm2(const TVec4<T>& v) { return v*v; }
template<class T> inline T norm(const TVec4<T>& v)  { return sqrt(norm2(v)); }

template<class T> inline void unitize(TVec4<T>& v)
{
    T l = norm2(v);
    if( l!=1.0 && l!=0.0 )  v /= sqrt(l);
}

template<class T> inline TVec3<T> proj(const TVec4<T>& v)
{
    TVec3<T> u(v[0], v[1], v[2]);
    if( v[3]!=1.0 && v[3]!=0.0 )
	u /= v[3];
    return u;
}

typedef TVec4<double> Vec4;
typedef TVec4<float>  Vec4f;

// GFXVEC4_INCLUDED
#endif
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