CGAL users discussion list

["Laurent Rineau (CGAL/GeometryFactory)" <>]

Le lundi 14 janvier 2013 12:37:53 thedorkknight a écrit :
> Laurent - many thanks to you.
> 
> i am still confused about the data type the points must be having. I am
> reading a .txt file in c++ then converting the individual lines which are
> strings to float variable type, which are saved in a vector, one vector for
> each dimension.I am getting an error feedback.
> 
> all the examples in the documentation seem to be reading in a *.cin file.
> using fstream. so i assume that even those are strings. does CGAL convert
> these values to numbers?

I have the impression that you do not know the I/O functions of the C++ 
standard library. For example, the following program:

#include <iostream>
int main() {
  double x;
  std::cin >> x;
  if(!std::cin) return 1; // exit with an error if the reading failed
  std::cout << "The read value is: " << x << std::endl;
  return 0;
}

read a 'double' from the standard input, and display the same value on the 
standard output.

Most CGAL objects have support for I/O operations. For example:

#include <iostream>
#include <CGAL/Simple_cartesian.h>

typedef CGAL::Simple_cartesian<double>::Point_2 Point_2;
int main() {
  Point_2 p;
  std::cin >> p;
  if(!std::cin) return 1;
  std::cout << "The point is: " << p << std::endl;
  return 0;
}

does the same for a 2D point. In that case, a valid input is:
  -2.3 5
and then the read point is the 2D point (-2.3, 5.0).

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/