added second part of evaluation in cpp

gnuplot-iostream/example-interactive.cc

@@ -0,0 +1,63 @@
+/*
+Copyright (c) 2013 Daniel Stahlke
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+
+#include <vector>
+#include <cmath>
+#include <cstdlib>
+
+#include <boost/tuple/tuple.hpp>
+
+// This must be defined before the first time that "gnuplot-iostream.h" is included.
+#define GNUPLOT_ENABLE_PTY
+#include "gnuplot-iostream.h"
+
+int main() {
+	Gnuplot gp;
+
+	// Create field of arrows at random locations.
+	std::vector<boost::tuple<double,double,double,double> > arrows;
+	for(size_t i=0; i<100; i++) {
+		double x = rand() / double(RAND_MAX);
+		double y = rand() / double(RAND_MAX);
+		arrows.push_back(boost::make_tuple(x, y, 0, 0));
+	}
+
+	double mx=0.5, my=0.5;
+	int mb=1;
+	while(mb != 3 && mb >= 0) {
+		// Make the arrows point towards the mouse click.
+		for(size_t i=0; i<arrows.size(); i++) {
+			double x = arrows[i].get<0>();
+			double y = arrows[i].get<1>();
+			double dx = (mx-x) * 0.1;
+			double dy = (my-y) * 0.1;
+			arrows[i] = boost::make_tuple(x, y, dx, dy);
+		}
+
+		gp << "plot '-' with vectors notitle\n";
+		gp.send1d(arrows);
+
+		gp.getMouse(mx, my, mb, "Left click to aim arrows, right click to exit.");
+		printf("You pressed mouse button %d at x=%f y=%f\n", mb, mx, my);
+		if(mb < 0) printf("The gnuplot window was closed.\n");
+	}
+}