我有几个关于boost :: regex的问题:我尝试了下面的一个例子。正则表达式不返回任何结果
1)什么是sregex_token_iterator的第4个参数?它听起来像一个“默认匹配”,但你为什么要这样做,而不是什么都不返回?我尝试没有第四个参数,但它不编译。
2)我得到的输出: (1,0) (0,0) (3,0) (0,0) (5,0)
谁能解释一下会出错?
#include <iostream>
#include <sstream>
#include <vector>
#include <boost/regex.hpp>
// This example extracts X and Y from (X , Y), (X,Y), (X, Y), etc.
struct Point
{
int X;
int Y;
Point(int x, int y): X(x), Y(y){}
};
typedef std::vector<Point> Polygon;
int main()
{
Polygon poly;
std::string s = "Polygon: (1.1,2.2), (3, 4), (5,6)";
std::string floatRegEx = "[0-9]*\\.?[0-9]*"; // zero or more numerical characters as you want, then an optional '.', then zero or more numerical characters.
// The \\. is for \. because the first \ is the c++ escpape character and the second \ is the regex escape character
//const boost::regex r("(\\d+),(\\d+)");
const boost::regex r("(\\s*" + floatRegEx + "\\s*,\\s*" + floatRegEx + "\\s*)");
// \s is white space. We want this to allow (2,3) as well as (2, 3) or (2 , 3) etc.
const boost::sregex_token_iterator end;
std::vector<int> v; // This type has nothing to do with the type of objects you will be extracting
v.push_back(1);
v.push_back(2);
for (boost::sregex_token_iterator i(s.begin(), s.end(), r, v); i != end;)
{
std::stringstream ssX;
ssX << (*i).str();
float x;
ssX >> x;
++i;
std::stringstream ssY;
ssY << (*i).str();
float y;
ssY >> y;
++i;
poly.push_back(Point(x, y));
}
for(size_t i = 0; i < poly.size(); ++i)
{
std::cout << "(" << poly[i].X << ", " << poly[i].Y << ")" << std::endl;
}
std::cout << std::endl;
return 0;
}
你尝试libpcre? – 2012-01-13 17:37:53
我不想介绍更多的依赖关系。 – 2012-01-13 20:50:07