Functions¶

Include¶

Built-in C++ system library

#include <libraryname>

local library

#include "libraryname.h"

Using¶

using namespace /*name*/;

Many libraries separate their symbols (variables, functions, etc.) into namespaces to avoid conflicts
using namespace brings symbols from a library's namespace into the global scope （全局作用域）
- Common usage: using namespace std;
若不使用 using 声明，在调用函数时需要加上 <namespace name>:: 前缀

std::cout << "Hello, world!" << std::endl;

Console I/O¶

`cout`¶

int age = 20;
cout << "I'm " << age << " years old." << endl;

`cin`¶

不太推荐，因为没有输入格式检查。

课程中使用 Stanford Library 里的函数。

Function name	Example
`getInteger("Prompt")`	`int age = getInteger("How old are you? ");`
`getReal("Prompt")`	`double gpa = getReal("少废话，你 GPA 多少？ ");`
`getLine("Prompt")`	`string name = getLine("What's your name? ");`
`getYesOrNo("Prompt")` `getYesOrNo("Prompt", "y", "n")`	`if (getYesOrNo("R U single? ")) {...}`

Forward declarations¶

在函数定义之前声明函数，也称为函数原型（function prototype）

returnType functionName(parameters); //有分号

Default parameters¶

returnType functionName(parameters = defaultValue);

e.g.

// Print a line of characters of the given length
void printLine(int length = 5, char ch = '*'){
    for (int i = 0; i < length; i++){
        cout << ch;
    }
}

int main(){
    printLine(); // *****
    printLine(3); // ***
    printLine(4, '#'); // ####
}

Recursive Functions¶