Template.doc

Templates 定义一个模板使用的关键字：class和typename。在定义作为模板的时候：class和typename，作用是一样的。一 函数模板1 定义方式template function_declaration;template function_declaration;2 Exampletemplate T GetMax (T a, T b) T result;result = (ab)? a : b;return (result);3 使用方法function_name (parameters);int x,y;GetMax (x,y);对于内部类型，通常是可以无需制定具体的类型，编译器会自动识别，而是写成：int x,y;GetMax(x,y);/x，y为相同的类型int x;long y;GetMax(x,y);/x，y为不相同的类型 报错 两种不同的内部类型必须：template T GetMin (T a, U b) return (ab?a:b);int i,j;long l;i = GetMin (j,l);/或者i = GetMin (j,l);二 Class Template通常是使用模板作为类成员变量的类型1 Example：template class mypair T values 2; public: mypair (T first, T second)/内联函数 values0=first; values1=second; ;mypair myobject (115, 36);/这样使用mypair myfloats (3.0, 2.18);2 成员函数为非内联函数template class mypair T a, b; public: mypair (T first, T second) a=first; b=second; T getmax ();template /增加此声明T mypair:getmax () T retval; retval = ab? a : b; return retval;int main () mypair myobject (100, 75); cout myobject.getmax(); return 0;模板类成员函数外部定义方法：template T mypair:getmax ()三 模板特化 Template Specialization1 将模板类转化为特定类型相关的类/ class template:template class mycontainer T element; public: mycontainer (T arg) element=arg; T increase () return +element;/ class template specialization:template /class mycontainer /将其特例化为char型 char element; public: mycontainer (char arg) element=arg; char uppercase () if (element=a)&(element=z) element+=A-a; return element; ;int main () mycontainer myint (7); mycontainer mychar (j); cout myint.increase() endl; cout mychar.uppercase() endl; return 0;template class mycontainer . ;/模板类template class mycontainer . ;/特例化为char型template class mycontainer . ;/特例化为int型模板来与之相应的特例化的类之间，并不是什么继承关系，所以在特例化一个模板类时，需要将其所有的包含成员进行重写，可以进行扩展。2 非模板类型参数Non-type parameters for templatestemplate /int Nclass mysequence T memblock N; public: void setmember (int x, T value); T getmember (int x);template void mysequence:setmember (int x, T value) memblockx=value;template T mysequence:getmember (int x) return memblockx;int main () mysequence myints; mysequence myfloats; myints.setmember (0,100); myfloats.setmember (3,3.1416); cout myints.getmember(0) n; cout myfloats.getmember(3) n; return 0;可以设置模板类型的缺省值：template class mysequence .;mysequence myseq;/可以缺省使用 mysequence myseq;/等同于上面四 Templates and multiple-file projectsFrom the point of view of the compiler, templates are not normal functions or classes. They are compiled on demand, meaning that the code of a template function is not compiled until an instantiation with specific template arguments is required. At that moment, when an instantiation is required, the compiler generates a function specifically for those arguments from the template.模板不会在代码编译的时候直接进行编译，而是在被实例化一个特定类型的模板时候，才会编译到，生成一个特定参数的函数。When projects grow it is usual to split the code of a program in different source code files. In these cases, the interface and implementation are generally separated. Taking a library of functions as example, the interface generally consists of declarations of the prototypes of all the functions that can be called. These are generally declared in a header file with a .h extension, and the implementation (the definition of these functions) is in an independent file with c+ code. Because templates are compiled when required, this forces a restriction for multi-file projects: the implementation (definition) of a template class or function must be in the same file as its declaration. That means that we cannot separate the interface in a separate header file, and that we must include both interface and implementation in any file that uses the templates. 由于模板特殊的编译需要，模板类的定义和函数实现必须在同一个文件中进行。Since no code is generated until a template is instantiated when required, compilers are prepared to allow the inclusion more than once of the same template file with both declarations and definitions in a project without generating linkage errors.二 typename定义一个模板使用的关键字：class和typename。在定义作为模板的时候：class和typename，作用是一样的。使用typename，实际上也是为模板服务的，在某些情况下我们需要明确的指出某些变量为模板。1 在一个模板类中使用另一个模板类定义一个变量时templatestruct first typedef T * pointer;templateclass second first:pointer p; / syntax error （VC+中 并不报错）;In a template, the name of a member of another class that depends on its template parameter(s) (first:pointerin this example, dependent on theTparameter) is adependent namethat i