still confused about call by reference

[Derek Parnell]

On Mon, 29 Oct 2007 04:32:44 +0100, Hoenir wrote:

> I'm still a bit confused about call by reference. When do I have to 
> explicitly use the & operator and when to use in, out and inout?
> I want to convert my C++ vector struct to D:
> 
> struct vec3
> {
> 	vec3 operator+(const vec3& v) const
> 	{return vec3(x+v.x, y+v.y, z+v.z);}
> 	vec3 operator-(const vec3& v) const
> 	{return vec3(x-v.x, y-v.y, z-v.z);}
> 
> I'm also wondering about how to handle the constness.
> Thanks in advance for any help :)

I'm no C++ user so I'm guessing a bit with the C++ syntax, but I'd code
something like ...

module vecs;
struct vec3(VT)
{
    private VT x,y,z;
    
    vec3 opAdd(const ref vec3 v)
    {

        vec3 t;
    	
        t.x = x + v.x;
        t.y = y + v.y;
        t.z = z + v.z;
        return t;
    	
    }
    
    vec3 opSub(const ref vec3 v)
    {
        vec3 t;

        t.x = x - v.x;
        t.y = y - v.y;
        t.z = z - v.z;
    	
        return t;
    }
    
    void opCall(T,U,V)(const T a, const U b, const V c)
    {
        x = cast(VT)a;
        y = cast(VT)b;
        z = cast(VT)c;
    }
    
    
    private import std.string;
    string toString()
    {
        return std.string.format("[%s; %s; %s]", x,y,z);
    }
}

**** EXCEPT **** that 'const ref' crashes the compiler (see Bugzilla 1319)

  http://d.puremagic.com/issues/show_bug.cgi?id=1319


-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
29/10/2007 2:58:45 PM