C ++模板专业化语法 [英] C++ templates specialization syntax
问题描述
在C ++ Primer Plus(2001,Czech Translation)中,我发现了这些不同的模板特化语法:
function template
模板< typename T> void foo(T);
专业化语法
void foo(int param); // 1
void foo< int>(int param); // 2
template<> void foo< int>(int param); // 3
template<> void foo(int param); // 4
template void foo(int param); // 5
Googling一点,我发现只有No.3的例子。他们之间有什么区别(在调用,编译,使用)?其中有些是过时的还是过时的?为什么不使用第一?
以下是每种语法的注释:
void foo(int param); //不是一个特殊化,它是一个重载
void foo< int>(int param); // ill-formed
//这种形式总是工作
template<> void foo< int>(int param); //显式专门化
//与上面一样,但只有在模板参数可以扣除时才有效!
模板<> void foo(int param); //显式专门化
//与上面一样,但只有在模板参数可以扣除时才有效!
template void foo(int param); //显式实例化
p>
//注意< int> ;.这种形式总是工作!
template void foo< int>(int param); // explicit instantiation
//注意<> ;.只有模板参数扣除是可行的!
template void foo<>(int param); //显式实例化
因此,不要使函数模板特殊化:
- 为什么不专业化功能模板?
- < a href =http://www.gotw.ca/gotw/049.htm>模板专业化和重载
em>显式实例化
查看此:
In C++ Primer Plus (2001, Czech Translation) I have found these different template specialization syntax:
function template
template <typename T> void foo(T);
specialization syntax
void foo(int param); // 1
void foo<int>(int param); // 2
template <> void foo<int>(int param); // 3
template <> void foo(int param); // 4
template void foo(int param); // 5
Googling a bit, I have found only No.3 examples. Is there any difference (in call, compiling, usage) among them? Are some of them obsolete/deprecated? Why not just use No.1?
Here are comments with each syntax:
void foo(int param); //not a specialization, it is an overload
void foo<int>(int param); //ill-formed
//this form always works
template <> void foo<int>(int param); //explicit specialization
//same as above, but works only if template argument deduction is possible!
template <> void foo(int param); //explicit specialization
//same as above, but works only if template argument deduction is possible!
template void foo(int param); //explicit instantiation
Added by me:
//Notice <int>. This form always works!
template void foo<int>(int param); //explicit instantiation
//Notice <>. works only if template argument deduction is possible!
template void foo<>(int param); //explicit instantiation
From coding point of view, overload is preferred over function-template-specialization.
So, don't specialize function template:
And to know the terminologies:
- instantiation
- explicit instantiation
- specialization
- explicit specialization
See this :
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