这个模板怎么错了？

[chenhaifeng88888]

	else return m;

..\BasicFunction\ExternalSort.cpp:271: error: no matching function for call to `generateRuns(const std::basic_string<char, std::char_traits<char>, std::allocator<char> >&, int&, const bio_analysis::SearchEngineType&)'






#include <iostream>

using namespace std;

template<typename T>
T _m(int x)
{
	int k = 1;
	double m = 10.001;
	if(x == 1) return k;
	else return m;

}

int main() {
	_m<int>(1);
	_m<double>(2);
}


**** Build of configuration Debug for project ResultParser ****

**** Internal Builder is used for build               ****
g++ -O0 -g3 -Wall -c -fmessage-length=0 -oBasicFunction\ExternalSort.o ..\BasicFunction\ExternalSort.cpp
In file included from ..\BasicFunction\../bio_analysis_sdk.h:7,
                 from ..\BasicFunction\ExternalSort.h:4,
                 from ..\BasicFunction\ExternalSort.cpp:2:
..\BasicFunction\../../include/sdk.h: In member function `void proteomics_sdk::CSpectrum::Create_Hash_Table()':
..\BasicFunction\../../include/sdk.h:1002: warning: converting to `size_t' from `double'
..\BasicFunction\../../include/sdk.h: In member function `void proteomics_sdk::CSimpleMatchResult::track(const proteomics_sdk::CSpectrum&, const proteomics_sdk::CPeptideResult&, size_t, proteomics_sdk::CCondition&)':
..\BasicFunction\../../include/sdk.h:1068: warning: comparison between signed and unsigned integer expressions
..\BasicFunction\ExternalSort.cpp: In function `int generateRuns(std::string, int, const bio_analysis::SearchEngineType&)':
..\BasicFunction\ExternalSort.cpp:91: error: no matching function for call to `GetKey(bio_analysis::CMatchSpectraInfo&, const bio_analysis::SearchEngineType&)'
..\BasicFunction\ExternalSort.cpp:134: error: no matching function for call to `GetKey(bio_analysis::CMatchSpectraInfo&, const bio_analysis::SearchEngineType&)'
..\BasicFunction\ExternalSort.cpp: In function `void kwaymerge(int, int, int, const bio_analysis::SearchEngineType&)':
..\BasicFunction\ExternalSort.cpp:191: error: no matching function for call to `GetKey(bio_analysis::CMatchSpectraInfo&, const bio_analysis::SearchEngineType&)'
..\BasicFunction\ExternalSort.cpp:207: error: no matching function for call to `GetKey(bio_analysis::CMatchSpectraInfo&, const bio_analysis::SearchEngineType&)'
..\BasicFunction\ExternalSort.cpp: In function `int Merge(int, int, const bio_analysis::SearchEngineType&)':
..\BasicFunction\ExternalSort.cpp:240: error: no matching function for call to `kwaymerge(const int&, int&, int&, const bio_analysis::SearchEngineType&)'
..\BasicFunction\ExternalSort.cpp:248: error: no matching function for call to `kwaymerge(int&, int&, int&, const bio_analysis::SearchEngineType&)'
..\BasicFunction\ExternalSort.cpp: In function `void ExternalSort(const std::string&, size_t, const std::string&, const bio_analysis::SearchEngineType&, const int&)':
..\BasicFunction\ExternalSort.cpp:271: error: no matching function for call to `generateRuns(const std::basic_string<char, std::char_traits<char>, std::allocator<char> >&, int&, const bio_analysis::SearchEngineType&)'
Build error occurred, build is stopped
Time consumed: 2297  ms.  

[老邓]

T _m(int x)
必须返回T的类型

[老邓]

if(x == 1) return k;
else return m;
这个判断里的两个return类型不同，所以只能有一个为T类型，当然编译不通过了。

[大前置]

我在VC6.0下编译没有问题

[ToBeTough]

DEV c++中，这个能执行
#include <iostream>
using namespace std;
template<typename T>
T _m(int x)
{
int k = 1;
double m = 10.001;
if(x == 1) return k;
else return m;
}
int main() {
_m<double>(2);
return 0;
}
这个不能：
#include <iostream>
using namespace std;
template<typename T>
T _m(int x)
{
int k = 1;
double m = 10.001;
if(x == 1) return k;
else return m;
}
int main() {
_m<int>(1);
return 0;
}
为什么?

[owldestiny]

是类型转换的问题，这样写在Dev中就可以编译通过了
#include <iostream>

using namespace std;

template<typename T>
T _m(int x)
{
int k = 1;
double m = 10.001;
T temp;
if(x == 1) temp =static_cast<T>(k);
else temp = static_cast<T>(m);
return temp;

}

int main() {
cout<<_m<int>(1)<<endl;
cout<<_m<double>(2)<<endl;
system("PAUSE");
}

[yshuise]

#include <iostream>

using namespace std;

template<typename T>
T _m(int x)
{
    int k = 1;
    double m = 10.001;
    if(x == 1) return k;
    else return m;

}

你这样写的局限行太大。没有利用函数模板的自己的推导功能，而且使用不方便。

[pengzhixi]

template<typename T>
T _m(int x)
看你的错误信息，不是出在这个模版，这个模版只是产生了一个警告信息。

[Walf_ghoul]

可以尝试下5楼的做法。。。但是感觉这个模板局限性很大。。