// higher order function version 
// but still not MSP
public class HigherOrder2 {
    public static class TimesTwo implements ILambda<Double,Double> {
	public Double apply(Double param) { return param*2; }
    }

    public static class PlusFour implements ILambda<Double,Double> {
	public Double apply(Double param) { return param+4; }
    }

    public static class SquareRoot implements ILambda<Double,Double> {
	public Double apply(Double param) { return Math.sqrt(param); }
    }

    public static void printTable(ILambda<Double,Double> f,
				  double x1, double x2, int n) {
	assert n>1;

	double x = x1;
	double delta = (x2-x1)/(double)(n-1);

	// f.apply(x) just means what f(x) means in math!
	System.out.println("x                      f(x)");
	System.out.printf("%20.10f %20.10f\n", x, f.apply(x));
	for(int i=0; i<(n-1); ++i) {
	    x += delta;
	    System.out.printf("%20.10f %20.10f\n", x, f.apply(x));
	}
    }

    public static void main(String[] args) {
	printTable(new TimesTwo(), -5, 5, 11);
	printTable(new PlusFour(), -5, 5, 11);
	printTable(new SquareRoot(), -5, 5, 11);

	// anonymous inner class
	// We define a new ILambda from Double to Double
	// without giving it a name. When we do that, we
	// need to fill in all the methods that are still
	// abstract. Here, it is just the apply method.
	printTable(new ILambda<Double,Double>() {
	    public Double apply(Double param) {
		return param*param;
	    }
	}, -5, 5, 11);
    }
}