how to use variables in C++ in the gnuplot-iostream - c++

Question

I am using gnuplot-iostream for c++,my problem is like below:
gp << "set object 1 rect from 3,1 to 3.2,4 fc lt 1 \n";
In the numbers of above, can we use some variables in c++ to replace them? and how to do that? Adding one rectangle is easy, but when I want to add more, that will be very intractable.
I try several ways ,but it does not work.
Thanks ahead!

Answer 1

Never used gnuplot-iostream, but maybe some vanilla C++ will help you, iostream is just a pipe to console, so you cant interrupt the buffer but concatenate information, you could do something like this:
gp << "set object " << 1 << " rect from "
<< 3,1 << " to " << 3.2 << "," << 4 << " fc lt 1 \n";
But i suppose you don't want to do that.
I'd create a struct and overload the << operator to return whatever you need.
struct Rect {
float from[2];
float to[2];
}
std::ostream& operator<<(std::ostream& os, const Rect& obj)
{
std::string formated = "from "
+ std::to_string(obj.from[0]) + ","
+ std::to_string(obj.from[1]) + " to "
+ std::to_string(obj.to[0]) + ","
+ std::to_string(obj.to[1]);
os << formated;
return os;
}
So you can just define rectangles and pass them to the stream
Rect r1 = {{2,41},{63,1.4}};
std::cout << r1; // "from 2,41 to 63,1.4"