abstract class Expr {
public abstract Expr d
(String v
); public Expr plus(Expr e2) { return new Plus(this, e2); }
public Expr times(Expr e2) { return new Times(this, e2); }
}
class Int extends Expr {
private final int n;
public Int(int m) { n = m; }
public Expr d
(String v
) { return new Int
(0); } }
class Var extends Expr {
public Var
(String v
) { var
= v
; } public Expr d
(String v
) { return new Int
(var.
equals(v
) ? 1 : 0); } public String toString
() { return var
; } }
class Plus extends Expr {
private final Expr e1, e2;
public Plus(Expr a, Expr b) { e1 = a; e2 = b; }
public Expr d
(String v
) { return new Plus
(e1.
d(v
), e2.
d(v
)); } public String toString
() { return "(" + e1
+ " + " + e2
+ ")"; } }
class Times extends Expr {
private final Expr e1, e2;
public Times(Expr a, Expr b) { e1 = a; e2 = b; }
{ return new Plus(new Times(e1, e2.d(v)), new Times(e1.d(v), e2)); }
public String toString
() { return "(" + e1
+ " * " + e2
+ ")"; } }
public class Derivative {
public static void main
(String[] args
) { Expr x = new Var("x"), a = new Var("a"),
b = new Var("b"), c = new Var("c");
Expr e = a.times(x).times(x).plus(b.times(x)).plus(c);
System.
out.
println("d(" + e
+ ", x) = " + e.
d("x")); }
}
//java/4551