下面这个句子是什么

dandanzhang 2009-03-23 02:21:39

typename MxBlock <T>::iterator end() { return begin()+size(); }
typename MxBlock <T>::const_iterator end() const { return begin()+size(); }
关于MxBlock的定义如下代码所示：
template<class T>
class MxBlock
{
private:
int N;
T *block;

protected:
MxBlock() { }
void init_block(int n)
{
// Allocate memory for block
N=n; block = (T *)malloc(sizeof(T)*n);

// Initialize each entry
for(int i=0;i<n;i++) new((void *)&block[i],ARRAY_ALLOC_INPLACE) T;
}
void resize_block(int n)
{
T *old = block;

// Allocate new block
block = (T *)realloc(old, sizeof(T)*n);

// Initialize all the newly allocated entries
for(int i=N;i<n;i++) new((void *)&block[i],ARRAY_ALLOC_INPLACE) T;

N = n;
}
void free_block()
{
#if defined(_MSC_VER)
// The Microsoft compiler has a problem with the
// standard syntax below. For some reason,
// expanding it into the following pointer-based
// version makes it work. Don't ask me why.
//
for(int i=0; i<N; i++) { T *p = &block[i]; p->~T(); }
free(block);
#else
// Call the relevant destructors for each element before
// freeing the block. Has now effect for types like 'int'.
//
for(int i=0; i<N; i++) block[i].~T();
free(block);
#endif
}

public:
MxBlock(int n) { init_block(n); }
~MxBlock() { free_block(); }

operator const T*() const { return block; }
operator T*() { return block; }
int length() const { return N; }

#ifndef HAVE_CASTING_LIMITS
T& operator[](int i) { return block[i]; }
const T& operator[](int i) const { return block[i]; }
operator const T*() { return block; }
#endif

// These parenthesized accessors are included for backwards
// compatibility. Their continued use is discouraged.
//
T& operator()(int i) { return (*this)[i]; }
const T& operator()(int i) const { return (*this)[i]; }

// Primitive methods for altering the data block
//
void resize(int n) { resize_block(n); }
void bitcopy(const T *a, int n) // copy bits directly
{ memcpy(block, a, MIN(n,N)*sizeof(T)); }
void copy(const T *a, const int n) // copy using assignment operator
{ for(int i=0; i<MIN(n,N); i++) block[i] = a[i]; }
void bitcopy(const MxBlock<T>& b) { bitcopy(b, b.length()); }
void copy(const MxBlock<T>& b) { copy(b, b.length()); }

// Restricted STL-like interface for interoperability with
// STL-based code.
//
typedef T value_type;
typedef value_type *iterator;
typedef value_type *const_iterator;

int size() const { return length(); }

iterator begin() { return block; }
const_iterator begin() const { return block; }
iterator end() { return begin()+size(); }
const_iterator end() const { return begin()+size(); }
};
请问向上面这个类模板中定义的这个iterator在g++b编译时会遇到什么问题

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