// IfThenElse.hpp
1?
#pragma?once
?2?
?3?
template<bool?C>,?typename?Ta,?typename?Tb>
?4?
class?IfThenElse;
?5?
?6?
template<typename?Ta,?typename?Tb>
?7?
class?IfThenElse<true,?Ta,?Tb>
?8?
{
?9?
public:
10?
?????typedef?Ta?ResultT;
11?
};
12?
13?
template<typename?Ta,?typename?Tb>
14?
class?IfThenElse<false,?Ta,?Tb>
15?
{
16?
public:
17?
?????typedef?Tb ResultT;
18?
};
//這個IfThenElse模板估計以后要經常用到
// Sqrt.hpp
#pragma once
#include "IfThenElse.hpp"
?1?template<int?Num,?int?LOW?=?0,?int?HIGH?=?Num>
?2?class?Sqrt
?3?{
?4?public:
?5??????//?calculate?mid?value
?6??????enum
?7???????{
?8???????????mid?=?(LOW?+?HIGH?+?1)?/?2,
?9??????};
10???????
11???????//?二分法
12???????typedef?typename?IfThenElse<?(Num?<?mid?*?mid)
13??,?Sqrt<Num,?LOW,?mid?-?1>
14??,?Sqrt<Num,?mid,?HIGH>?
15??>::ResultT?SubT;
16??
17?????????enum
18?????????{
19?????????????result?=?SubT::result;
20?????????};
21??};
22??
23??template<int?Num,?int?M>
24??class?Sqrt<Num,?M,?M> // 偏特化，作為終止
25?{
26?public:
27??????enum
28??????{
29?????????result?=?M,
30???????};
31?};
讓我們測試一下
std::cout<< "Sqrt<25>::result = " << Sqrt<25>::result << std::endl;
?1?template<int?Num,?int?LOW?=?0,?int?HIGH?=?Num>
?2?class?Sqrt
?3?{
?4?public:
?5??????//?calculate?mid?value
?6??????enum
?7??????{
?8??????????mid?=?(LOW?+?HIGH?+?1)?/?2,
?9??????};
10??????
11??????//?二分法
12??????typedef?typename?IfThenElse<?(Num?<?mid?*?mid)
13?,?Sqrt<Num,?LOW,?mid?-?1>
14?,?Sqrt<Num,?mid,?HIGH>?
15?>::ResultT?SubT;
16?
17????????enum
18????????{
19????????????result?=?SubT::result;
20????????};
21?};
22?
23?template<int?Num,?int?M>
24?class?Sqrt<Num,?M,?M>posted on 2006-10-27 09:45
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