Template.doc

Templates 定義一個(gè)模板使用的關(guān)鍵字：class和typename。在定義作為模板的時(shí)候：class和typename，作用是一樣的。一 函數(shù)模板1 定義方式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);對于內(nèi)部類型，通常是可以無需制定具體的類型，編譯器會(huì)自動(dòng)識(shí)別，而是寫成：int x,y;GetMax(x,y);/x，y為相同的類型int x;long y;GetMax(x,y);/x，y為不相同的類型 報(bào)錯(cuò) 兩種不同的內(nèi)部類型必須：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通常是使用模板作為類成員變量的類型1 Example：template class mypair T values 2; public: mypair (T first, T second)/內(nèi)聯(lián)函數(shù) values0=first; values1=second; ;mypair myobject (115, 36);/這樣使用mypair myfloats (3.0, 2.18);2 成員函數(shù)為非內(nèi)聯(lián)函數(shù)template class mypair T a, b; public: mypair (T first, T second) a=first; b=second; T getmax ();template /增加此聲明T mypair:getmax () T retval; retval = ab? a : b; return retval;int main () mypair myobject (100, 75); cout myobject.getmax(); return 0;模板類成員函數(shù)外部定義方法：template T mypair:getmax ()三 模板特化 Template Specialization1 將模板類轉(zhuǎn)化為特定類型相關(guān)的類/ class template:template class mycontainer T element; public: mycontainer (T arg) element=arg; T increase () return +element;/ class template specialization:template /class mycontainer /將其特例化為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 . ;/模板類template class mycontainer . ;/特例化為char型template class mycontainer . ;/特例化為int型模板來與之相應(yīng)的特例化的類之間，并不是什么繼承關(guān)系，所以在特例化一個(gè)模板類時(shí)，需要將其所有的包含成員進(jìn)行重寫，可以進(jìn)行擴(kuò)展。2 非模板類型參數(shù)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;可以設(shè)置模板類型的缺省值：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.模板不會(huì)在代碼編譯的時(shí)候直接進(jìn)行編譯，而是在被實(shí)例化一個(gè)特定類型的模板時(shí)候，才會(huì)編譯到，生成一個(gè)特定參數(shù)的函數(shù)。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. 由于模板特殊的編譯需要，模板類的定義和函數(shù)實(shí)現(xiàn)必須在同一個(gè)文件中進(jìn)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定義一個(gè)模板使用的關(guān)鍵字：class和typename。在定義作為模板的時(shí)候：class和typename，作用是一樣的。使用typename，實(shí)際上也是為模板服務(wù)的，在某些情況下我們需要明確的指出某些變量為模板。1 在一個(gè)模板類中使用另一個(gè)模板類定義一個(gè)變量時(shí)templatestruct first typedef T * pointer;templateclass second first:pointer p; / syntax error （VC+中 并不報(bào)錯(cuò)）;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