c++官方文檔

　　來自官方文檔。。。感謝老王指出需要c++11,一下代碼全在c++11下編譯,編譯參數加入  -std=c++11

#include<stdio.h>
#include<iostream>
#include<queue>
#include<map>
#include<memory.h>
#include <math.h>
#include <stdlib.h>
#include <algorithm>
#include <climits>
#include <sstream>
using namespace std;

int main(const int argc, char** argv)
{
	//c style
	int i = 0;
	//c++ style
	int j(1);
	//only in c++ 11
	int k = { 2 };
	cout << i << endl;
	cout << j + k << endl;
	int foo = 0;
	//same as int bar=foo;
	auto bar = foo;
	cout << bar << endl;
	//bar2 type is int,has no initVal
	decltype(foo) bar2;
	bar2 = 4.2000;
	cout << bar2 << endl;
	cout << sizeof(wchar_t) << endl;
	//base 10
	int ii = 10;
	//base 8
	int kk = 010;
	//base 16
	int kkk = 0xff;
	cout << ii << " " << kk << " " << kkk << endl;
	int kkkk = 75; //int
	unsigned int uik = 4294967295u; //unsigned int
	long lk = 75l; //long
	long ulk = 75ul; //unsigned long
	cout << kkkk << " " << uik << " " << lk << " " << ulk << endl;
	cout << "long double size " << sizeof(long double) << endl;
	cout << "long long int size " << sizeof(long long int) << endl;
	//default type for floating-point literals is double
	//we can add suffix f or l
	float fi = 6.02e23f;	//float
	long double ld = 3.14159L;	//long double
	cout << "fi " << fi << " long double " << ld << endl;
	//Internally, computers represent characters as numerical codes
	//計算機本質上將字符表示成數字
	string x = "string expressed in \
     two lines";
	cout << x << endl;
	//All the character literals and string literals described above are made of characters of type char
	//所有字符和字符串字面量都是由char組成,可以加下面的前綴
	//u  char16_t
	//U  char32_t
	//L  wchar_t
	//string字面量可以加以下前綴
	//u8 The string literal is encoded in the executable using UTF-8
	//執行時用utf-8編碼
	//R 	The string literal is a raw string
	//表示原始的string
	string ss = R"(string with \backslash)";
	string sss = "(string with \backslash)";
	cout << ss << endl;
	cout << sss << endl;
	//c++已經存在三個字面量  true false nullptr
	cout << "bool" << sizeof(bool) << " sizeof nullptr" << sizeof(nullptr)
			<< endl;
	bool footrue = true;
	bool foofalse = false;
	int* p = nullptr;
	cout << footrue << endl;
	cout << foofalse << endl;
	//&p p的地址
	//*p p指向內存的內容
	//p p這塊內存中的值
	cout << p << endl;
	cout << "&p " << &p << endl;
	int** pp = &p;
	cout << pp << endl;
	//有魔力的語法
	//根據文檔的描述 c++內置三個字面量 true,false nullptr
	cout << (false == nullptr) << endl;
	//顯示轉換
	int ci;
	float cf = 3.14;
	//繼承自 c
	ci = (int) cf;
	//c++ style
	ci = int(cf);
	//The value returned by sizeof is a compile-time constant, so it is always determined before program execution.
	//sizeof返回編譯時的常量,所以這個值永遠都在執行前確定
	string mystr("123465 456 79");
	int myint;
	//標准頭文件sstream定義了一種叫做stringstream的類型,允許把string作為輸入流
	stringstream sin(mystr);
	//流已經到末尾
	string mystr2;
	while (sin >> myint)
		cout << myint << " ";
	cout << endl;
	getline(stringstream(mystr), mystr2);
	cout<<mystr2<<endl;
	return 0;
}