算是模板使用的一種技巧

用模板當(dāng)數(shù)組元素參數(shù)維度?

#include <stdexcept>template <typename T, int MAXSIZE> class Stack {private:T elems[MAXSIZE]; // elementsint numElems; // current number of elementspublic:Stack(); // constructorvoid push(T const&); // push elementvoid pop(); // pop elementT top() const; // return top elementbool empty() const { // return whether the stack is emptyreturn numElems == 0;}bool full() const { // return whether the stack is fullreturn numElems == MAXSIZE;} };// constructor template <typename T, int MAXSIZE> Stack<T,MAXSIZE>::Stack (): numElems(0) // start with no elements {// nothing else to do }template <typename T, int MAXSIZE> void Stack<T,MAXSIZE>::push (T const& elem) {if (numElems == MAXSIZE) {throw std::out_of_range("Stack<>::push(): stack is full");}elems[numElems] = elem; // append element++numElems; // increment number of elements }template<typename T, int MAXSIZE> void Stack<T,MAXSIZE>::pop () {if (numElems <= 0) {throw std::out_of_range("Stack<>::pop(): empty stack");}--numElems; // decrement number of elements }template <typename T, int MAXSIZE> T Stack<T,MAXSIZE>::top () const {if (numElems <= 0) {throw std::out_of_range("Stack<>::top(): empty stack");}return elems[numElems-1]; // return last element }

使用時就可以根據(jù)需要指定最大的元素個數(shù),不用造成資源的浪費

#include <iostream> #include <string> #include <cstdlib> #include "stack4.hpp"int main() {try {Stack<int,20> int20Stack; // stack of up to 20 intsStack<int,40> int40Stack; // stack of up to 40 intsStack<std::string,40> stringStack; // stack of up to 40 strings// manipulate stack of up to 20 intsint20Stack.push(7);std::cout << int20Stack.top() << std::endl;int20Stack.pop();// manipulate stack of up to 40 stringsstringStack.push("hello");std::cout << stringStack.top() << std::endl; stringStack.pop();stringStack.pop();}catch (std::exception const& ex) {std::cerr << "Exception: " << ex.what() << std::endl;return EXIT_FAILURE; // exit program with ERROR status} }

注意:被實例化出來的int20Stack和int40Stack不可以隱式轉(zhuǎn)換.

模板成員參數(shù)

template <typename T, int VAL> T addValue (T const& x) {return x + VAL; }

特化的參數(shù)，用于不在于類型,直接適用于函數(shù)中

注意點:浮點類型不可以作為nontype template parameters

以下定義是錯誤的

//error template <double T> double process(double v) {return v*T; } 超強干貨來襲 云風(fēng)專訪：近40年碼齡，通宵達旦的技術(shù)人生

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