Certain functions

What do most people do when creating functions such as vector or quaternion normalizers? I mean, do they usually return the new vector / quat. or automatically set the vector to it? Thanks for any opinions :D !

I would imagine passing the vector to the function as a reference/pointer would be faster than returning it, as you don't have to create a variable for returning. So if the code is in a hurry I would guess the pointer makes more sense.

i usually pass a pointer argument and use set it directly. this can have problems in dlls i think

I think in general it's best not to create so many copies and just use it when you have to. Here's an old piece of code that demonstrates a typical canonical form used often with C++ objects (though some of the maths are probably off). The underlying implementation is written much like normal C functions. This just makes it more flexible (though it would be even better to place the functions in an 'extern "C" {' block, and get rid of any other C++ artifacts, too, like by switching the references with pointers, etc).

Code:

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#ifndef VECTOR_C
#define VECTOR_C


 namespace psi
{

/* 'vector' is a 3D point object */

 struct vector
{
 vector(double x0 = 0, double y0 = 0, double z0 = 0);
 
  inline
 vector &
  set(double x0, double y0, double z0);
 
  inline 
 vector &
  operator () (double x0, double y0, double z0);
 
  inline 
 vector &
  operator = (const vector & other);
 
  inline 
 vector &
  add(const vector & other);
 
  inline 
 vector &
  operator += (const vector & other);

  inline
 vector &
  subtract(const vector & other);
 
  inline 
 vector &
  operator -= (const vector & other); 

  inline 
 vector &
  multiply(const vector & other);
 
  inline
 vector &
  operator *= (const vector & other);

  inline     
 vector &
  divide(const vector & other);

  inline   
 vector &
  operator /= (const vector & other); 
 
  inline
 const vector
  plus(const vector & other) const;
 
  inline 
 const vector
  operator + (const vector & other) const;
 
  inline 
 const vector
  minus(const vector & other) const;

  inline 
 const vector
  operator - (const vector & other) const;

  inline 
 const vector
  times(const vector & other) const;

  inline 
 const vector
  operator * (const vector & other) const;

  inline 
 const vector
  quotient(const vector & other) const;

  inline 
 const vector
  operator / (const vector & other) const;

  inline 
 double
  product(const vector & other) const;

  inline 
 double
  angle(const vector & other) const;
 
  inline 
 double
  product() const;

  inline 
 double
  length() const;

  inline 
 vector &
  normalize();
 
  friend
 ostream &
  operator << (ostream & stream, vector & value)
 {
  return stream << "x( " << value.x << " )  y( " << value.y << " )  z( " << value.z << " )";
 }     
 
  friend
 istream &
  operator >> (istream & stream, vector & value)
 {
    while(!(stream >> value.x))
    {
    stream.clear();
    stream.ignore();
    }
    while(!(stream >> value.y))
    {
    stream.clear();
    stream.ignore();
    }

    while(!(stream >> value.z))
    {
    stream.clear();
    stream.ignore();
    }

 if(stream.peek() == '\n')
  stream.get();
 
 return stream;
}     
public:
 double x, y, z;
};


/* C-style inline functions */


 inline
vector &
 add(vector & dest, const vector & a, const vector & b)
{
 dest.x = a.x + b.x;
 dest.y = a.y + b.y;
 dest.z = a.z + b.z;
 return dest;
}

 inline
vector &
 add(vector & dest, const vector & src)
{
 return add(dest, dest, src);
}

 inline
vector &
 subtract(vector & dest, const vector & a, const vector & b)
{
 dest.x = a.x - b.x;
 dest.y = a.y - b.y;
 dest.z = a.z - b.z;
 return dest;
}

 inline
vector &
 subtract(vector & dest, const vector & src)
{
 return subtract(dest, dest, src);
}

 inline
vector &
 multiply(vector & dest, const vector & a, const vector & b)
{
 dest.x = a.x * b.x;
 dest.y = a.y * b.y;
 dest.z = a.z * b.z;
 return dest;
}

 inline
vector &
 multiply(vector & dest, const vector & src)
{
 return multiply(dest, dest, src);
}

 inline
vector &
 divide(vector & dest, const vector & a, const vector & b)
{
 dest.x = b.x == 0 ? 0 : a.x / b.x;
 dest.y = b.y == 0 ? 0 : a.y / b.y;
 dest.z = b.z == 0 ? 0 : a.z / b.z;
 return dest;
}

 inline
vector &
 divide(vector & dest, const vector & src)
{
 return divide(dest, dest, src);
}

 inline 
const vector
 plus(const vector & a, const vector & b)
{
 vector temp(a);

 return vector(temp.add(b));
} 
 
 inline 
const vector
 minus(const vector & a, const vector & b)
{
 vector temp(a);

 return vector(temp.subtract(b));
} 
 
 inline 
const vector
 times(const vector & a, const vector & b) 
{
 vector temp(a);

 return vector(temp.multiply(b));
} 
 
 inline 
const vector
 quotient(const vector & a, const vector & b)
{
 vector temp(a);

 return vector(temp.divide(b));
} 

 inline
double
 product(const vector & a, const vector & b)
{
 return (a.x * b.x) + (a.y * b.y) + (a.z * b.z);
} 

 inline
double
 product(const vector & a)
{
 return product(a, a);
} 

 inline 
double
 length(const vector & a)
{
 return sqrt(product(a));
}

 inline
vector &
 normalize(vector & a)
{
 double length = a.length();
 
 vector temp(length, length, length);
 
 return a.divide(temp);
}

/* ??Yarghh! */

 inline
double
 angle(const vector & a, const vector & b)
{
 double al = a.length(), bl = b.length();
 
 return al && bl ? acos(product(a, b)/(al * bl)) : 0;
} 


/* The implementation uses the inline C-style functions */


vector::
 vector(double x0, double y0, double z0)
{
 set(x0, y0, z0);
}

 vector &
vector::
 set(double x0, double y0, double z0)
{
 x = x0, y = y0, z = z0;
 
 return *this; 
}
 
 vector &
vector::
 operator () (double x0, double y0, double z0)
{
 return set(x0, y0, z0);
}
 
 vector &
vector::
 operator = (const vector & other)
{
 return set(other.x, other.y, other.z);
}
 
 vector &
vector::
 add(const vector & other)
{
 return psi::add(*this, other);
}

 vector &
vector::
 operator += (const vector & other)
{
 return psi::add(*this, other);
}
 
 vector &
vector::
 subtract(const vector & other)
{
 return psi::subtract(*this, other);
}

 vector &
vector::
 operator -= (const vector & other)
{
 return psi::subtract(*this, other);
}

 vector &
vector::
 multiply(const vector & other)
{
 return psi::multiply(*this, other);
}

 vector &
vector::
 operator *= (const vector & other)
{
 return psi::multiply(*this, other);
}

 vector &
vector::
 divide(const vector & other)
{
 return psi::divide(*this, other);
}

 vector &
vector::
 operator /= (const vector & other)
{
 return psi::divide(*this, other);
}

 const vector
vector::
 plus(const vector & other) const
{
 return psi::plus(*this, other);
} 
 
 const vector
vector::
 operator + (const vector & other) const
{
 return psi::plus(*this, other);
} 
 
 const vector
vector::
 minus(const vector & other) const
{
 return psi::minus(*this, other);
} 
 
 const vector
vector::
 operator - (const vector & other) const
{
 return psi::minus(*this, other);
}   
 
 const vector
vector::
 times(const vector & other) const
{
 return psi::times(*this, other);
}
 
 const vector
vector::
 operator * (const vector & other) const
{
 return psi::times(*this, other);
}
 
 const vector
vector::
 quotient(const vector & other) const
{
 return psi::quotient(*this, other);
}
 
 const vector
vector::
 operator / (const vector & other) const
{
 return psi::quotient(*this, other);
}

 double
vector::
 product(const vector & other) const
{
 return psi::product(*this, other);
} 

 double

vector::
 product() const
{
 return psi::product(*this);
} 

 double
vector::
 length() const
{
 return psi::length(*this);
}

 vector &
vector::
 normalize()
{
 return psi::normalize(*this);
}

 double
vector::
 angle(const vector & other) const
{
 return psi::angle(*this, other);
}


} // namespace

 
#endif // VECTOR_C

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