public double eval(final double... args) {
		final double val = apply(box(args));
		return val == -0.0 ? 0.0 : val;
	}
Convenient method, which lets you apply the program function without
explicitly create a wrapper array.

{@snippet lang="java":
 final double result = MathExpr.parse("2*z + 3*x - y").eval(3, 2, 1);
 assert result == 9.0;
}

@see #apply(Double[])
@see #eval(String, double...)

@param args the function arguments
@return the evaluated value
@throws NullPointerException if the given variable array is {@code null}
@throws IllegalArgumentException if the length of the argument array
        is smaller than the program arity
jenetics.prog/src/main/java/io/jenetics/prog/op/MathExpr.java