用Xcode来写C++程序[4] 函数
此节包括引用函数,内联函数,防止修改函数入参,函数自身带有默认值.
引用函数:防止复制对象,减少系统开销
内联函数:编译的时候根据具体情形将代码嵌入进去,成不成功编译器说了算,减少系统开销提升性能
引用函数(防止篡改初始值的入参声明方式):防止修改数据源
函数参数带有默认值:函数的某个参数可以给定默认值,精简函数的使用
最简单的函数
#include <iostream> using namespace std; int addition (int a, int b) { return a + b; } int main () { int z; z = addition (5,3); cout << "The result is " << z << endl; }
打印结果
The result is 8 Program ended with exit code: 0
传递引用(int& 表示)
#include <iostream> using namespace std; void duplicate (int& a, int& b, int& c) { a *= 2; b *= 2; c *= 2; } int main () { int x = 1, y = 3, z = 7; duplicate (x, y, z); cout << "x=" << x << ", y=" << y << ", z=" << z << endl; return 0; }
打印结果
x=2, y=6, z=14 Program ended with exit code: 0
防止篡改数据源(const 修饰变量)
#include <iostream> #include <string> using namespace std; string concatenate (const string& a, const string& b) { return a + b; } int main () { string x = "You"; string y = "XianMing"; cout << concatenate(x, y) << endl; return 0; }
打印结果
YouXianMing Program ended with exit code: 0
内联函数(减少函数调用开销)
#include <iostream> #include <string> using namespace std; inline string concatenate (const string& a, const string& b) { return a + b; } int main () { string x = "You"; string y = "XianMing"; cout << concatenate(x, y) << endl; return 0; }
打印结果
YouXianMing Program ended with exit code: 0
带默认值的函数(如果不赋值,则有一个默认值)
#include <iostream> using namespace std; int divide (int a, int b = 2) { int r; r = a / b; return (r); } int main () { cout << divide (12) << endl; cout << divide (20, 4) << endl; return 0; }
打印结果
YouXianMing Program ended with exit code: 0
函数先声明,后使用
#include <iostream> using namespace std; void odd (int x); void even (int x); int main() { int i; do { cout << "Please, enter number (0 to exit): "; cin >> i; odd (i); } while (i!=0); return 0; } void odd (int x) { if ((x%2)!=0) cout << "It is odd.\n"; else even (x); } void even (int x) { if ((x%2)==0) cout << "It is even.\n"; else odd (x); }
递归调用
#include <iostream> using namespace std; long factorial (long a) { if (a > 1) return (a * factorial (a-1)); else return 1; } int main () { long number = 9; cout << number << "! = " << factorial (number); return 0; }
打印结果
9! = 362880 Program ended with exit code: 0
原文：http://www.cnblogs.com/YouXianMing/p/4322843.html