试着写了个class template，编译错误，说是库文件里有错误，我总不能帮borland debug吧，挺纳闷儿的，请大家看看。

[kaitree]

试着写了个class template，编译错误，说是库文件里有错误，我总不能帮borland debug吧，挺纳闷儿的，请大家看看。

我的代码:
//test.h
#include <iostream.h>

template <class T>
class Test
{
private:
T total;
public:
set(T t1, T t2){total = t1 + t2;}
};

编译情况:
D:\C++\code\friends>bcc32 test.h
Borland C++ 5.6 for Win32 Copyright (c) 1993, 2002 Borland
test.h:
Error E2257 C:\Program Files\Borland\CBuilder6\Include\stl/_mbstate.h
52: , expected
Error E2453 C:\Program Files\Borland\CBuilder6\Include\stl/type_traits
.h 64: Size of the type '__true_type' is unknown or zero
Error E2453 C:\Program Files\Borland\CBuilder6\Include\stl/type_traits
.h 65: Size of the type '__false_type' is unknown or zero
Error E2141 C:\Program Files\Borland\CBuilder6\Include\stl/type_traits
.h 68: Declaration syntax error
Error E2141 C:\Program Files\Borland\CBuilder6\Include\stl/type_traits
.h 70: Declaration syntax error
Error E2141 C:\Program Files\Borland\CBuilder6\Include\stl/type_traits
.h 73: Declaration syntax error
Error E2141 C:\Program Files\Borland\CBuilder6\Include\stl/type_traits
.h 77: Declaration syntax error

...........

.h 235: Declaration syntax error
Error E2228 C:\Program Files\Borland\CBuilder6\Include\stl/type_traits
.h 235: Too many error or warning messages
*** 26 errors in Compile ***

[kaitree]

噢，我找到问题了，谢谢各位，看来大家都喜欢用GUI的IDE哈。

[fangrk]

#include <iostream>
using namespace std;


template <class T>
class Test
{
private:
T total;
public:
set(T t1, T t2){total = t1 + t2;}
};

int main()
{

}

编译没有问题

[kaitree]

如果注释掉第一行中的 iostream.h 如下:
//#include <iostream.h>

template <class T>
class Test
{
private:
T total;
public:
set(T t1, T t2){total = t1 + t2;}
};

则编译情况如下:

D:\C++\code\friends>bcc32 test.h
Borland C++ 5.6 for Win32 Copyright (c) 1993, 2002 Borland
test.h:
Error E2141 test.h 3: Declaration syntax error
*** 1 errors in Compile ***
===============
到底是怎么稿第嘛?

[kaitree]

自己发现只要光编译.h的文件就会有以上错误信息，但是为什么呢？
.h文件也许不能单独被编译，可错误信息也很怪呀，如何导致这样的信息的勒？

[layman2008]

vc 6.0下没问题

[greenspan]

CB5下我试了一下，没错，我的代码
File1.h中
///////////////////////////////////
#include <iostream.h>

template <class T>
class Test
{
private:
T total;
public:
set(T t1, T t2){total = t1 + t2;}
T Total()const{return total;}
};
Form1中
//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop
#include <iostream.h>
#include "Unit1.h"
#include "File1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;

//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)
{
}
//---------------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)
{

Test<int> t;
t.set(10,20);
Caption=t.Total();

}
//---------------------------------------------------------------------------
输出也正常

[greenspan]

增加#include <string>后
把Button1Click中的代码改为
Test<std::string> t;
t.set(std::string("I love "),std::string("you!"));
Caption=t.Total().c_str();
也正常

模板的错误是有点怪的，不过一般是由于你的实例化错误引起的

[kaitree]

嗯，看来一定要有个main在.h文件里面，才能正常编译。