网站建设胶州,中国政务网站建设绩效评估,百度推广免费建站,站酷网app目录 一#xff1a;IO流的继承关系#xff1a;
二#xff1a;输入输出功能
1. 基本用法 2. 格式化输入
3.非格式化输入
4. 格式化输出
三#xff1a;流
1. 字符流
2. 向字符流中写入数据
3. 从字符流中读出数据
4. 清空字符流
5.完整的例子
四#xff1a;文件…目录 一IO流的继承关系
二输入输出功能
1. 基本用法 2. 格式化输入
3.非格式化输入
4. 格式化输出
三流
1. 字符流
2. 向字符流中写入数据
3. 从字符流中读出数据
4. 清空字符流
5.完整的例子
四文件流 一IO流的继承关系 类含义basic_streambuf 读取或写入数据ios_base独立于字符类型的流属性basic_ios依赖于字符类型的流属性basic_istream用于读取数据的流基类basic_iostream用于写入数据的流基类basic_iostream用于读写数据的流基类
二输入输出功能
typedef basic_istreamchar istream;
typedef basic_ostreamchar ostream;
1. 基本用法 #include iostream
int main(){
std::cout Type in your numbers;
std::cout (Quit with an arbitrary character): std::endl;
// 2000 Enter 11 a
int sum{0};
int val;
while (std::cin val) sum val;
std::cout Sum: sum; // Sum: 2011
} 2. 格式化输入
include iostreamint main()
{int a, b;std::cout Two natural numbers: std::endl;std::cin a b; // 2000 11std::cout a: a b: b;
}
3.非格式化输入
#include iostreamint main()
{std::string line;std::cout Write a line: std::endl;std::getline(std::cin, line); // Only for testing purpose.std::cout line std::endl; // Only for testing purpose.std::cout Write numbers, separated by; std::endl;while (std::getline(std::cin, line, ;) ) {std::cout line ;}
}
4. 格式化输出
#include iostreamint main()
{int num{2011};std::cout.setf(std::ios::hex, std::ios::basefield);std::cout num std::endl; // 7dbstd::cout.setf(std::ios::dec, std::ios::basefield);std::cout num std::endl; // 2011std::cout std::hex num std::endl; // 7dbstd::cout std::dec num std::endl; // 2011
}
#include iostream
#include fstream
#include iomanip
#include iostreamint main()
{std::cout.fill(#);std::cout -12345;std::cout std::setw(10) -12345; // ####-12345std::cout std::setw(10) std::left -12345; // -12345####std::cout std::setw(10) std::right -12345; // ####-12345std::cout std::setw(10) std::internal -12345; //-####12345std::cout std::oct 2011; // 3733std::cout std::hex 2011; // 7dbstd::cout std::showbase;std::cout std::dec 2011; // 2011std::cout std::oct 2011; // 03733std::cout std::hex 2011; // 0x7dbstd::cout 123.456789; // 123.457std::cout std::fixed;std::cout std::setprecision(3) 123.456789; // 123.457std::cout std::setprecision(6) 123.456789; // 123.456789std::cout std::setprecision(9) 123.456789; // 123.456789000std::cout std::scientific;std::cout std::setprecision(3) 123.456789; // 1.235e02std::cout std::setprecision(6) 123.456789; // 1.234568e02std::cout std::setprecision(9) 123.456789; // 1.234567890e02std::cout std::hexfloat;std::cout std::setprecision(3) 123.456789; // 0x1.edd3c07ee0b0bp6std::cout std::setprecision(6) 123.456789; // 0x1.edd3c07ee0b0bp6std::cout std::setprecision(9) 123.456789; // 0x1.edd3c07ee0b0bp6std::cout std::defaultfloat;std::cout std::setprecision(3) 123.456789; // 123std::cout std::setprecision(6) 123.456789; // 123.457std::cout std::setprecision(9) 123.456789; // 123.456789}
三流
1. 字符流
//String stream for the input of data of type char and wchar_t.
std::istringstream and std::wistringstream//String stream for the output of data of type char and wchar_t.
std::ostringstream and std::wostringstream//String stream for the input or output of data of type char and wchar_t.
std::stringstream and std::wstringstream2. 向字符流中写入数据
std::stringstream os;
os New String;
os.str(Another new String);
3. 从字符流中读出数据
std::string os;
std::string str;
os str;
str os.str();
4. 清空字符流
std::stringstream os;
os.str();
5.完整的例子
#include iostream
#include fstream
#include iomanip
#include iostream
#include sstreamtemplate typename T
T StringTo(const std::string source) {std::istringstream iss(source);T ret;iss ret;return ret;
}template typename T
std::string ToString(const T n) {std::ostringstream tmp;tmp n;return tmp.str();
}int main()
{std::cout 5 StringToint(5); // 5std::cout 5 6 StringToint(5) 6; // 11std::cout ToString(StringToint(5) 6); // 11std::cout 5e10: std::fixed StringTodouble(5e10); // 50000000000
}
四文件流
//File stream for the input of data of type char and wchar_t.
std::ifstream and std::wifstream//File stream for the output of data of type char and wchar_t.
std::ofstream and std::wofstream//File stream for the input and output of data of type char and wchar_t.
std::fstream and std::wfstream//Data buffer of type char and wchar_t.
std::filebuf and std::wfilebuf#include fstreamint main()
{std::ifstream in(inFile.txt);std::ofstream out(outFile.txt);out in.rdbuf();
}
#include fstream
#include iostream
#include istream
#include stringvoid writeFile(const std::string name) {std::ofstream outFile(name);if (!outFile) {std::cerr Could not open file name std::endl;exit(1);}for (unsigned int i 0; i 10; i) {outFile i 0123456789 std::endl;}
}int main()
{std::string random{ random.txt };writeFile(random);std::ifstream inFile(random);if (!inFile) {std::cerr Could not open file random std::endl;exit(1);}std::string line;std::cout inFile.rdbuf();// 0 0123456789// 1 0123456789// 9 0123456789std::cout inFile.tellg() std::endl; // 200inFile.seekg(0); // inFile.seekg(0, std::ios::beg);std::getline(inFile, line);std::cout line; // 0 0123456789inFile.seekg(20, std::ios::cur);std::getline(inFile, line);std::cout line; // 2 0123456789inFile.seekg(-20, std::ios::end);std::getline(inFile, line);std::cout line; // 9 0123456789
}
五IO流运算符重载支持用户自定义类型输入输出
friend std::istream operator (std::istream in, Fraction frac);
friend std::ostream operator (std::ostream out, const Fraction frac);
#include fstream
#include iostream
#include istream
#include stringclass Fraction {
public:Fraction(int num 0, int denom 0) :numerator(num), denominator(denom) {}friend std::istream operator (std::istream in, Fraction frac);friend std::ostream operator (std::ostream out, const Fraction frac);
private:int numerator;int denominator;
};
std::istream operator (std::istream in, Fraction frac) {in frac.numerator;in frac.denominator;return in;
}
std::ostream operator (std::ostream out, const Fraction frac) {out frac.numerator / frac.denominator;return out;
}int main()
{Fraction frac(3, 4);std::cout frac; // 3/4std::cout Enter two numbers: ;Fraction fracDef;std::cin fracDef; // 1 2std::cout fracDef; // 1/2}
