c++ primer（第五版）筆記 第三章（1）string類

//#define NDEBUG

#include<iostream>
#include<string>
#include<cassert>

//using namespace std;
//using 聲明不應該出現在頭文件中，會使每個包含頭文件的文件都會有這個聲明，造成名字衝突
using std::cout;
using std::cin;
using std::endl;
using std::string;

void string_learn();
void practice_3_6();
void practice_3_7();
void practice_3_10();

int main()
{
	//string_learn();
	practice_3_6();
	practice_3_7();
	practice_3_10();
	return 0;
}

void string_learn()
{
	//string 構造函數
	
	//(1) Default constructor. Constructs empty string (zero size and unspecified capacity)
	//默認構造函數，構造空字符串（0大小，未指定容量）
	//------------------------------------------------------------------------------
	//explicit basic_string();  
	//------------------------------------------------------------------------------
	string s;
	assert( s.empty() && ( s.length() == 0) && ( s.size() == 0));

	//(2) Constructs the string with count copies of character ch.The behavior is undefined if count >= npos
	//用 count 個字符 ch 構造一個字符串，如果 count 大於 npos, 行爲未定義
	//npos 是 string 類中定義的一個保證大於任何有效下標的值，類型 string::size_type( unsigned int), 大於該值意思就是超出範圍的無效下標
	//------------------------------------------------------------------------------
	//basic_string( size_type count, CharT ch);
	//------------------------------------------------------------------------------
	string s2(5, '*');
	cout << string::npos << endl;
	cout << "s2:" << s2 << endl;
	//(3) Constructs the string with a substring [pos, pos+count) of other. If the requested substring lasts past the end of the string, or if count == npos, the resulting substring is [pos, size())
	//用字符串 other 的 pos 到 ( pos + count - 1 ) 位構造字符串，如果請求的子串超出了原字符串，或者 count 大於 npos, 結果爲 pos 到 （ size() - 1 ) 位, pos 從 0 開始計算
	//------------------------------------------------------------------------------
	//basic_string(const basic_string& other, size_type pos, size_type count = std::basic_string::npos);
	//------------------------------------------------------------------------------
	string const sTmp("string test!");
	string s3(sTmp, 2);
	cout << "s3:" <<  s3 << endl;
	//(4) Constructs the string with the first count characters of character string pointed to by s. s can contain null characters. The behavior is undefined if s does not point at an array of at least count elements of CharT
	//用c風格字符串指針 s 指向的字符串的前 count 個字符構造字符串，s 可以包含空白字符， 如果 s 指向的字符串長度不足 count，其行爲是未定義的
	//------------------------------------------------------------------------------
	//basic_string( const CharT* s, size_type count)
	//------------------------------------------------------------------------------
	string s4("hello world", 2);
	cout << "s4:" << s4 << endl;

	//(5) Constructs the string with the contents initialized with a copy of the null-terminated character string pointed to by s. The length of the string is determined by the first null character. The behavior is undefined if s does not point at an array of at least Traits::length(s)+1 elements of CharT.
	//用c風格字符串的指針 s 所指向的一個以空白符結束的字符串的副本構造字符串，字符串的長度由第一個空字符結束('\0')何時出現決定，如果 s 指向的字符串長度不足 Traits::length(s)+1，其行爲是未定義的
	//------------------------------------------------------------------------------
	//basic_string( const CharT* s )
	//------------------------------------------------------------------------------
	string s5("hello\0world");
	cout << "s5:" << s5 << endl;

	//(6) Constructs the string with the contents of the range [first, last). This constructor does not participate in overload resolution if InputIt does not satisfy InputIterator.
	//用迭代器 first 到 last - 2 表示範圍，注意 end() 返回下一個位置的指針
	//------------------------------------------------------------------------------
	//template< class InputIt >
	//basic_string( InputIt first, InputIt last)
	//------------------------------------------------------------------------------
	char charTmp[] = "HELLO WORLD";
	string s6(std::begin(charTmp) + 3, std::end(charTmp));
	cout << "s6:" << s6 << "!" << endl;

	//(7) Copy constructor. Constructs the string with the copy of the contents of other
	//拷貝構造函數，用另一個 string 對象的副本構造
	//------------------------------------------------------------------------------
	//basic_string( const basic_string& other )
	//------------------------------------------------------------------------------
	string s7(sTmp);
	cout << "s7:" << s7 << endl;

	//(8) Move constructor. Constructs the string with the contents of other using move semantics. other is left in valid, but unspecified state.
	//移動構造函數(待完善)
	//------------------------------------------------------------------------------
	//basic_string( basic_string&& other ) noexcept  (since C++11)
	//------------------------------------------------------------------------------
	string s8(string("hello ") + string("world"));
	cout << "s8:" << s8 << endl;

	//(9) Constructs the string with the contents of the initializer list init.
	//用初始化列表構造
	//------------------------------------------------------------------------------
	//basic_string( std::initializer_list<CharT> init)  (since C++11)
	//------------------------------------------------------------------------------
	string s9({ 'h', 'e', 'l', 'l', 'o' });
	cout << "s9:" << s9 << endl;

	//IO
	cin >> s >> s9; //以第一個不爲空的字符開始，到第一個空白處結束
	cout << s << " - "
		<< s9 << endl;

	//使用 getline 讀取一行，直到遇到換行符，讀入換行符，但不存入到 string 對象中
	while (getline(cin, s))
		cout << s << endl;

	//string::size_type類型，由 size() 返回的無符號整型而且可以放下任何 string 對象的大小
	//string 類定義的配套類型，體現了標準庫類型與機器無關的特性
	//注意在表達式中與帶符號數一起將產生意想不到的結果

	//用 == 和 ！= 檢測2個 string 對象是否相等，相等意味着它們的長度相同而且包含的字符也全都相同
	//關係運算符的比較規則：
	//1.如果2個 string 對象的長度不相同，而且較短的 string 對象的每個字符都與較長 string 對象對應位置上的字符相同，就說較短 string 對象小於較長string 對象
	//2.如果2個 string，結果由2者第一對相異字符的字典順序決定

	//可以使用 = 將一個 string 對象賦給另一個
	string str(10, 'x');
	string s10 = str;

	//可以使用 + 拼接2個 string 對象，或者拼接1個 string 對象和1個字符（串）字面值，當把 string 對象和字符字面值及字符串字面值混在一條語句中時，必須確保每個 + 符號的兩側運算對象有一個是 string 對象
	string s11 = "hello", s12 = "world", s13;
	//s13 = "hello" + "world"; 錯誤，不能把字面值直接相加
	s13 = s11 + " " + s12 + '\n';

	//關於字符特性的函數，定義於 cctype
	//isalnum(c): checks if a character is alphanumeric
	//isalpha(c): checks if a character is alphabetic
	//islower(c): checks if a character is lowercase
	//isupper(c): checks if a character is an uppercase character
	//isdigit(c): checks if a character is a digit
	//isxdigit(c): checks if a character is a hexadecimal character
	//iscntrl(c): checks if a character is a control character
	//isgraph(c): checks if a character is a graphical character
	//isspace(c): checks if a character is a space character
	//isblank(c): checks if a character is a blank character (C++11)
	//isprint(c): checks if a character is a printing character
	//ispunct(c): checks if a character is a punctuation character
	//tolower(c): converts a character to lowercase
	//toupper(c): converts a character to uppercase
		
	//範圍 for (range for)
	//語法： for (declaration : expression) {}

	//下標運算符[],接收 string::size_type 類型的值（下標或索引），表示要訪問的字符的位置，返回值是該位置上字符的引用
	//下標從 0 開始，必須大於等於 0，且小於 size(),超出此範圍的下標將引發不可預知的結果
}

void practice_3_6()
{
	string str("hello world");
	for (auto &c : str)
		c = 'X';
	cout << str << endl;
}

void practice_3_7()
{
	string str("hello world");
	for (char &c : str)
		c = 'X';
	cout << str << endl;
}

void practice_3_10()
{
	string str, sTmp;
	cin >> str;
	for (auto &c : str)
		if (!ispunct(c))
			sTmp += c;
	cout << sTmp << endl;
			
}