added example code

added better default range
fixed BIGDOUBLE to be closer to max double (used for default best fitness)

example.cpp

@@ -0,0 +1,43 @@
+#include <cstdio>
+
+#include "de.h"
+
+// just a helper function used in calculating the polynomails
+double Polynomial(double x, double a, double b, double c, double d)
+{
+	return a*(x*x*x) + b*(x*x) + c*x + d;
+}
+
+// the function we're searching for
+double TargetFunction(double input)
+{
+	return Polynomial(input,17.0,321.0,-2.0,324.0);
+}
+
+// our DE implementation
+class PolySearch: public DE::Engine<4>
+{
+	public:
+		double CalculateError(const double testcase[4], bool& stop)
+		{
+			double error = 0.0;
+			for ( int i=-100;i<=100;i++ )
+			{
+				double test   = Polynomial((double)i,testcase[0],testcase[1],testcase[2],testcase[3]);
+				double actual = TargetFunction((double)i);
+				error += (test-actual)*(test-actual);
+			}
+			if ( error < 0.00000000000001 )
+			{
+				stop = true;
+			}
+		}
+};
+
+// main program
+int main()
+{
+	PolySearch de;
+	de.Solve();
+	return 0;
+}