Simple C++ template definition problem
I'm new to C++. Here is the code:
template <class T> typename lw_slist {
// .... some code
private:
typedef struct _slist_cell {
_slist_cell *next;
T data;
} slist_cell;
lw_slist::slist_cell *root;
};
Give this compilation error:
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
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Why?
It's an error because that isn't any kind of declaration at all.
The compiler needs to know if you want a class
, struct
, enum
, union
or something else. typename
is not the right keyword to use there.
You are probably looking for this:
template<class T>
struct lw_slist {
};
A whole new question, a whole new answer:
I think that you will want it like this:
template <class T>
class lw_slist {
// .... some code
private:
struct slist_cell {
slist_cell *next;
T data;
};
slist_cell *root;
};
There is no reason to use a typedef: C++ makes classes and structs automatically part of the namespace.
There is no reason to use lw_slist::slist_cell because slist_cell is already in the current namespace.
The reason that you were getting the error dependent name is not a type
is that inside a template declaration C++ cannot tell if lw_slist<T>::slist_cell
is supposed to be a type or a variable. It assumes a variable named slist_cell
and you have to use typename
to say otherwise.
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