Simple gnuplot interface

plot.hpp

#include <span>
#include <memory>
#include <stdexcept>
#include <algorithm>

using vec2_t [[gnu::vector_size(8)]] =  float;

struct pipe_closer
{
	void operator()(FILE* f) const
	{
		if(f != nullptr)
		{ pclose(f); }
	}
};

using pipe = std::unique_ptr<FILE, pipe_closer>;

template<class ... T>
auto make_pipe(T&& ... args)
{
	auto ret = pipe{popen(std::forward<T>(args)...)};
	if(ret == nullptr)
	{ throw std::runtime_error{"Failed to start gnuplot"};}

	return ret;
}

struct axis_range
{
	double min;
	double max;
};

class plot
{
public:
	plot():m_handle{make_pipe("gnuplot -p", "w")}{}

	plot& x_range(axis_range range)
	{
		fprintf(m_handle.get(), "set xrange [%.17e:%.17e]\n", range.min, range.max);
		return *this;
	}

	plot& y_range(axis_range range)
	{
		fprintf(m_handle.get(), "set yrange [%.17e:%.17e]\n", range.min, range.max);
		return *this;
	}

	plot& axis_equal()
	{
		fprintf(m_handle.get(), "set size ratio -1\n");
		return *this;
	}

	plot& add_data_series(std::span<vec2_t const> points)
	{
		fprintf(m_handle.get(), "plot '-' with lines\n");
		std::ranges::for_each(points, [handle = m_handle.get()](auto point){
			fprintf(handle, "%.17e %.17e\n", point[0], point[1]);
		});
		fprintf(m_handle.get(), "e\n");
		return *this;
	}

private:
	pipe m_handle;
};