Little question:
is this correct (it compiles & works allright)
typedef struct vec3
{
float x,y,z;
} vec3
I'm just concerned because I see everywhere doing it this way:
typedef struct _vec3 // <--- '_'
{
float x,y,z;
} vec3
Why?
Use is for this:
typedef struct vec3
{
float x,y,z;
#ifdef __cplusplus
vec3() {}
vec3(float x,float y,float z) {
this->x=x; this->y=y; this->z=z;
}
#endif
} vec3;
So the constructors need vec3 in the 'typedef struct vec3' line.
Nothing wrong there?
typedef struct ...
Author
Hi!
typedef struct vec3{ float x,y,z;} vec3; Under C++ you don''t need the typedef. Also, the above code should cause an error under C++ because it in effect declares a variable with the same identifier as the type, kinda like int int or string string.
My C''s too rusty to give you an accurate description.
Further to Oluseyi's answer:
You need the typedef in C because what you're actually declaring is this:
Now, people get sick and tired of saying
...for their variables. Therefore, you typedef it like any other:
The two names should be different and the convention is to say "tagXYZ" (e.g. "struct tagSomething") or to put an underscore there. Also note that because it's a shortcut you need to use the full name if you're doing something such as linked lists:
You *don't* and *should not* put that typedef in for C++. In C++ structs are just like classes except that they start off in public rather than private mode (and default to public rather than private inheritance? I think).
[edited by - Alimonster on July 23, 2002 4:03:35 PM]
You need the typedef in C because what you're actually declaring is this:
struct _Something {}; Now, people get sick and tired of saying
struct _Something myStructName;struct _Something myStructName2; ...for their variables. Therefore, you typedef it like any other:
typdef struct _Something { define your stuff here } something; The two names should be different and the convention is to say "tagXYZ" (e.g. "struct tagSomething") or to put an underscore there. Also note that because it's a shortcut you need to use the full name if you're doing something such as linked lists:
typedef struct tagSomething{ struct tagSomething* next; // <-- notice full name there} Something; You *don't* and *should not* put that typedef in for C++. In C++ structs are just like classes except that they start off in public rather than private mode (and default to public rather than private inheritance? I think).
[edited by - Alimonster on July 23, 2002 4:03:35 PM]
Author
Thanks.
I use DevC++ and they compile just fine, in c and c++ I'v used it long with no problem :o
So what might be correct solution? It should work in c and c++ and have constructors in c++.
Maybe this?
Looks messy, is there simpler solution?
[edited by - stefu on July 23, 2002 4:51:16 PM]
I use DevC++ and they compile just fine, in c and c++ I'v used it long with no problem :o
So what might be correct solution? It should work in c and c++ and have constructors in c++.
Maybe this?
#ifdef __cplusplusstruct vec3 {#elsetypedef struct tag_vec3 {#endif float x,y,z;#ifdef __cplusplus vec3() {} vec3(float x,float y,float z) { ... }};#else} vec3;#endif Looks messy, is there simpler solution?
[edited by - stefu on July 23, 2002 4:51:16 PM]
Author
WOHOO, guess what I found from MS DX SDK? This (in d3dxmath.h):
It is just like I have done it
//--------------------------// 3D Vector//--------------------------typedef struct D3DXVECTOR3{#ifdef __cpluspluspublic: D3DXVECTOR3() {}; D3DXVECTOR3( const float * ); D3DXVECTOR3( const D3DVECTOR& ); D3DXVECTOR3( float x, float y, float z ); // casting operator float* (); operator const float* () const; operator D3DVECTOR* (); operator const D3DVECTOR* () const; operator D3DVECTOR& (); operator const D3DVECTOR& () const; // assignment operators D3DXVECTOR3& operator += ( const D3DXVECTOR3& ); D3DXVECTOR3& operator -= ( const D3DXVECTOR3& ); D3DXVECTOR3& operator *= ( float ); D3DXVECTOR3& operator /= ( float ); // unary operators D3DXVECTOR3 operator + () const; D3DXVECTOR3 operator - () const; // binary operators D3DXVECTOR3 operator + ( const D3DXVECTOR3& ) const; D3DXVECTOR3 operator - ( const D3DXVECTOR3& ) const; D3DXVECTOR3 operator * ( float ) const; D3DXVECTOR3 operator / ( float ) const; friend D3DXVECTOR3 operator * ( float, const struct D3DXVECTOR3& ); BOOL operator == ( const D3DXVECTOR3& ) const; BOOL operator != ( const D3DXVECTOR3& ) const;public:#endif //__cplusplus float x, y, z;} D3DXVECTOR3, *LPD3DXVECTOR3; It is just like I have done it
quote:Original post by stefu
...is there simpler solution?
C++ structs that use no C++-specific features are backwards compatible with C (up to C99; the C maintainers have decided that compatibility with C++ is not a major consideration of theirs, so C++ may retaliate and finally be shed of its legacy). Just define the struct C-style, but omit the tag (it typedefs an unnamed struct to vec3, and works in C++ too).
Author
quote:Original post by Oluseyi
Just define the struct C-style, but omit the tag (it typedefs an unnamed struct to vec3, and works in C++ too).
Like this?
typedef struct { float x,yz;} vec3; But now I cannot put there constructors
"ANSI c++ forbids declaration ''vec3'' with no type"
Maybe I stay in my original way (also the MS way).
It works!
quote:Original post by Oluseyi
Also, the above code should cause an error under C++ because it in effect declares a variable with the same identifier as the type, kinda like int int or string string.
Not quite. It doesn''t declare a variable, only a type alias (i.e. vec3 becomes an alias for vec3). It''s completely unnecessary (in C++ that is), but still valid for C compatibility reasons.
If you want constructor, and your source file is .CPP, why not just throw away your typedef-combos? 
Apart from knowing more, I don''t think these kind of construct really do something (accept that you want C-compatibility, which I don''t think that you are going for this).
Apart from knowing more, I don''t think these kind of construct really do something (accept that you want C-compatibility, which I don''t think that you are going for this).
Author
I''v come yet with another nice solution 
I think that this should work pretty well
// first pure c solutiontypedef struct _vec3{ float x,y,z;} vec3;// Derived class with c++ featuresclass Vector3 : public vec3 {public: // default constructor Vector3() {}; // another constructor Vector3(float _x,float _y,float _z) { x=_x; y=_y; z=_z;}; // copy constructor to allow: Vector3 a=v3; (where v3 is a vec3) Vector3(const vec3& v) { x=v.x; y=v.y; z=v.z;}; // put here all operators...}; I think that this should work pretty well
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