Give struct the status it deserves

Hasan Aljudy hasan.aljudy at gmail.com
Sat Mar 25 11:15:04 PST 2006


Hong wrote:
> Structs are second class citizens of... or maybe refugees of D, they are victims
> of discrimination.
> Following are the reasons:
> 
> 1. most D programmers don't use struct, unless they happen to be the poor guy
> writing the C interface.
> 
> 2. to use structs you have to use pointers, but the spec says pointers are only
> provided for C compatibility, structs are to be avoided as long as the world
> spins.
> 
> 3. pointers + overloaded operators make a mess.... this is a less offensive
> example: (*o) = (*t)[(*i) * (*j)] ... the pointers and operators are abusing
> each other.
> 
> 4. structs cannot have constructor, "static opCall" is best you can do.
> 
> 5. structs are more efficient? Not when structs are passed around by value. To
> change a struct member: 1. make a copy 2. change the copy 3. Copy the copy back
> into the original location. Two damned copies for.... efficiency.
> 
> 6. yes, you can use pointers to change a struct member without copying, if you
> can be bothered to define 2 accessor methods, one returns a copy another one
> returns a pointer.
> 
> 7. Most standard containers (DTL) do not allow a pointer to a contained struct
> to be retrieved, all changes, or just about anything has to be done via copies.
> 
> 8. structs have different behaviours between array and Vector, array [] returns
> a reference, Vector [] returns a copy, nice rookie trap.
> 
> 
> Imho, following are little suggestions for structs to make first class citizens
> of D:
> 
> 1. have some sort of reference semantic to replace pointers. Pointers are not
> necessary unless structs are used with "new"
> 
> 2. add constructor for struct, destructors are not necessary.
> 
> I use structs because I need efficiency and stack allocated data structures,
> however, it is painful to see a C++ program turns into a C like program when
> ported to D.
> 
> 

structs are a light wieght alternative to classes.
Seriously, if structs don't suffice for your needs, use classes! You 
won't lose /that/ much performance.



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