如何从文本文件中动态提取负数和正数？

Question

I have obtained a line in textfile that says for example:

XCoordRange=0-8

Now that would be easy, i can just do a simple ifstream and read it to a string line and proceed to map and convert

line[12] to int x1

and line[14] to int x2 .

This way, i am able to parse the values into my x1 and x2 coordinates.

However, things get tricky when different scenarios appear such as :

XCoordRange=-10--5 (both negative)

XCoordRange=-10-5 (one negative and one positive)

XCoordRange=10--5 (one positive and one negative)

So my question is how can i dynamically map numbers in different scenarios into my x1 and x2 ?

It seems as though i can only read one type of data (negative or positive) and not both (negative and positive).

Below is what i've tried so far:

    string line = "XCoordRange=-10-5";  
    size_t pos = 0;     
    string token;   
    string delimiter = "=";

    if(pos = line.find(delimiter) != string::npos)
    {
                    token = line.substr(0, pos);
                    line.erase(0, pos + delimiter.length());
    }

This gives me an output of -10--5 , however, i am stuck in what i should do next.

Answer 1

You can use istringstream defined in <sstream> as follows

// if line is "-10--5"
std::istringstream iss(line);
int n1, n2;
iss >> n1; // read first number ("-10")
iss.ignore(); // ignore the '-' character
iss >> n2; // read the second number ("-5")

Answer 2

   size_t equalPos = line.find("=");
   size_t dashPos = line.find("-", equalPos + 2);
   int x1 = stoi(line.substr(equalPos + 1, dashPos - equalPos - 1));
   int x2 = stoi(line.substr(dashPos + 1));

Of course, if you're not sure that the string line will always match the given pattern, then you need to add some checks.