[英]C++ Specify input from istream and test it
我有一个基本上表示一个元组(双倍x,双倍y)的类,并且我已经重载了<<操作符,以便可以打印该类。 现在,我想对>>做同样的事情,因此它仅支持以下格式:x,(x)和(x,y)。
我喜欢以下代码:
std::ostream & operator<< (std::ostream &output, tuple &c){
output << "(" << c.x << "," << c.y << ")" << endl;
return output;
}
std::istream & operator>> (std::istream & input, tuple &c){
// Check for following patterns: x, (x) or (x,y)
}
我可以遍历输入和正则表达式匹配吗? 在那种情况下怎么办? 还有我怎么能测试它是否真的在工作,像这样的std :: cin >>“(10.2,5.5)”
还是我需要从文件中读取内容进行测试?
编辑:给出的答案确实解决了这个问题,但是我想添加一种测试它的方法,因为它可能是使用我以外的人:
tuple x(6,2);
stringstream ss;
ss << x;
ASSERT_EQUALS(ss.str(), "(6,2)\n");
对于这样的简单输入任务,正则表达式将是不必要的。 这是我的方法,无需解析任何有效输入,只需解析即可:
std::istream & operator>> (std::istream & input, tuple &c){
// Check for following patterns: x, (x) or (x,y)
char firstCharacter;
input >> firstCharacter; // See what the first character is, since it varies
if (firstCharacter == '(')
{ // The simplest case, since the next few inputs are of the form n,n)
char delimiters;
input >> c.x >> delimiters >> c.y >> delimiters;
// N , N )
// You also here have to check whether the above inputs are valid,
// such as if the user enters a string instead of a number
// or if the delimeters are not commas or parentheses
}
else if (isdigit(firstCharacter) || firstCharacter == '-')
{ // For negative numbers
char delimiters;
input.unget(); // Put the number back in the stream and read a number
input >> c.x >> delimiters >> delimiters >> c.y >> delimiters;
// N , ( N )
// You also here have to check whether the above inputs are valid,
// such as if the user enters a string instead of a number
// or if the delimeters are not commas or parentheses
}
else
{
// Handle some sort of a parsing error where the first character
// is neither a parenthesis or a number
}
return input;
}
开派对有点晚,但是这里是正则表达式解决方案。 它虽然不漂亮,但允许输入负数以及科学计数法。 它还可以容忍数字之间的空格:
#include <iostream>
#include <regex>
#include <tuple>
std::istream &operator>> (std::istream &input, std::tuple<double, double> &t)
{
std::smatch m;
std::string s;
if (std::getline(input, s))
{
if (std::regex_match(s, m, std::regex(R"(\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)\s*)"))) //x
t = std::move(std::make_tuple(std::stod(m[1]), 0.0));
else if (std::regex_match(s, m, std::regex(R"(\s*\(\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)\s*\)\s*)"))) //(x)
t = std::move(std::make_tuple(std::stod(m[1]), 0.0));
else if (std::regex_match(s, m, std::regex(R"(\s*\(\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)\s*,\s*([-+]?\d*\.?\d+(?:[eE][-+]?\d+)?)\s*\)\s*)"))) //(x,y)
t = std::move(std::make_tuple(std::stod(m[1]), std::stod(m[2])));
}
return input;
}
int main()
{
std::tuple <double, double> t;
std::cout << "Enter data in format num, (num) or (num1,num2): ";
std::cin >> t;
std::cout << "Tuple 0: " << std::get<0>(t) << std::endl;
std::cout << "Tuple 1: " << std::get<1>(t) << std::endl;
return 0;
}
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