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constructor problem

Started by daniel_i_l Apr 21, 2006 at 2:27 AM 5 replies 500+ views

Original Post

Apr 21, 2006 at 2:27 AM

I have a struct like this: struct CVector3 { public: float x, y, z; }; And I have a lot of places in the program were I initialize like this: CVector3 vector = {0,0,0}; But when I make a constructor like this: struct CVector3 { public: float x, y, z; CVector3(float a, float b, float c){x=a; y=b; z=c;} }; It says that I cant initialize the same way that I did before and I have to use the constructor. Is any way to use both of the ways? Thanks.

Zahlman

Apr 21, 2006 at 2:48 AM

0) You should be implementing the constructor this way instead:

CVector3(float a, float b, float c) : x(a), y(b), z(c) {}

1) Using the constructor is as simple as 'CVector3 vector(0, 0, 0)', so why do you care?

hh10k

Apr 21, 2006 at 2:53 AM

I spent a bit fussing over this as well, but it's just one of those language quirks. Kind of like templated typedefs :)

dpadam450

Apr 21, 2006 at 3:00 AM

"Constructor" is for C++

class CVector
{
public:
x, y, z;
CVector(float a, float b, float c)
{
//blah
}
};

So the answer is no, unless by some crazy thing I dont know about C. And p.s, in a Struct everything is public, so you dont need to declare it public. Basically my guess is that if your compiler accepts the keyword "public" I would assume its mixing c/c++ code, and thats why it said the word 'constructor'.

Aardvajk

Apr 21, 2006 at 3:05 AM

There is no difference between a struct and a class in c++ except that a struct is public by default (to stop old code breaking) and a class is private by default. You can still have explicitly public and private sections in structs (and even protected AFAIK).

simon10k

Apr 21, 2006 at 3:07 AM

struct and class are the same in C++ apart from the default access being private in a class.

You can init your types like this too, same as you can do with build in types except that there are no user defined literals.

v = vector3D(0,0,0);

simon10k

Apr 21, 2006 at 3:08 AM

heh, you beat me to it =)

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