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我正在嘗試爲模板化爲整數值(不是類型)的函數編寫動態分派器。雖然我可以編寫代碼生成器或使用大型宏鏈來創建調度程序源,但似乎模板化解決方案會更加優雅。動態分派的部分模板專業化
我我的調度員剝離下來,以一個簡單的形式(這實際上並沒有做任何分派):
// works fine with full template specialization
template <int N>
struct TestDispatcher1D {
int f(int n) {
if (n == N) return n; // replace me with actual dispatch
TestDispatcher1D<N-1> t;
return t.f(n);
}
};
template<>
struct TestDispatcher1D<-1> {
int f(int n) { return -1; }
};
// partial template specialization is problematic
template <int M, int N>
struct TestDispatcher2D {
int f(int m, int n);
};
template<int M>
struct TestDispatcher2D<M,-1> {
int f(int m, int n) { return -1; }
};
template<int N>
struct TestDispatcher2D<-1,N> {
int f(int m, int n) { return -1; }
};
template<>
struct TestDispatcher2D<-1,-1> {
int f(int m, int n) { return -1; }
};
template <int M, int N>
int TestDispatcher2D<M,N>::f(int m, int n) {
if ((n == N) && (m == M)) return n + m; // replace me with actual dispatch
if (m < M) {
if (n < N) {
TestDispatcher2D<M-1,N-1> t;
return t(m,n);
} else {
TestDispatcher2D<M-1,N> t;
return t(m,n);
}
} else {
TestDispatcher2D<M,N-1> t;
return t(m,n);
}
}
// test code
void testIt() {
{
TestDispatcher1D<16> t;
t.f(16);
}
{
TestDispatcher1D<16>t;
t.f(0);
}
{
TestDispatcher2D<16,16>t;
t.f(8,8);
}
}
當GCC 4.1.1編譯,我得到以下錯誤:
t.cpp: In member function 'int TestDispatcher2D::f(int, int) [with int M = 16, int N = 16]': t.cpp:63: instantiated from here t.cpp:40: error: no match for call to '(TestDispatcher2D) (int&, int&)' t.cpp:63: instantiated from here t.cpp:43: error: no match for call to '(TestDispatcher2D) (int&, int&)' t.cpp:63: instantiated from here t.cpp:47: error: no match for call to '(TestDispatcher2D) (int&, int&)'
很顯然,當我嘗試創建遞歸對象時,編譯器不會將其視爲實例化新模板的請求。
有什麼建議嗎?
您也可以編寫TestDispatcher2D <...>().f(mn,n) – 2009-02-18 16:16:53