emulate java functors

May 17, 2008 06:36am pdt

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05.07.2008 at 04:46AM PDT, ID: 23382386

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7.2

emulate java functors

Zone: Java Programming Language

Hello Experts,

I strongly need your assistance how can this code be placed as a applyFunction() in the code in the code sippet:
interface Function {
intfun(intn);
}
class Sqrimplements Function {
public intfun(intn) { return n*n; }
}
class Cube implements Function {
public int fun(int n) { return n*n*n; }
}
...
intcompose(Function f, Function g, intx)
return f.fun(g.fun(x));
}
...
compose(new Sqr(), new Cube(), 7);

Thanks in advance for any help !

         
           
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             /*
 ******************************************
 * Interfaces with a single-method protocol 
 ******************************************
 */
interface NegInterface 
{
	public void applyNeg();
}
 
interface CosInterface
{
	public void applyCos();
}
 
interface SqrtInterface
{
	public void applySqrt();
}
 
interface SinInterface
{
	public void applySin();
}
 
 
class MathArray { 
 
	double[] array; 
 
	MathArray(double[] array) { 
 
		this.array = array; 
 
	} 
 
	public void applyFunction(int func)
	{
		switch (func)
		{
			case 0:
				applyNeg();
				break;
			case 1:
				applySqrt();
				break;
			case 2:
				applyCos();
				break;
			case 3:
				applySin();
				break;
			default:
				System.out.println("Invalid Option Selected \n Choose 0,1,2 or 3");
			break;
		}
	}
 
 
	void warnNaN(double d) { 
 
		if(((Double)d).isNaN()) 
			System.err.println("Warning: result is undefined"); 
 
	} 
 
 
	void applyNeg() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = -array[i]; 
 
			warnNaN(array[i]); 
 
		} 
	} 
 
	void applySqrt() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.sqrt(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void applySin() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.sin(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void applyCos() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.cos(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void print() { 
 
		for(int i = 0; i < array.length; i++) 
			System.out.print(array[i] + (i < array.length-1?", ":"\n")); 
 
	} 
 
} 
 
 
public class Test { 
 
	public static void main(String[] args) {
 
		MathArray te = new MathArray(new double[] { 0.1, 2.23, 3.08 });
 
		te.applyFunction(Integer.parseInt(args[0]));
 
		te.print();
	}
 
}

           
         

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Question Stats

Zone: Programming

Question Asked By: perdoname_

Solution Provided By: objects

Participating Experts: 1

Solution Grade: B

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05.07.2008 at 03:40PM PDT, ID: 21520979

Rank: Genius

objects:

try something like this:

interface UnaryFunction {
      public double f(double input);
}

class SinUnary implements UnaryFunction {
      public double f(double in) {
            return Math.sin(in);
      }
}

class MathArray {

      double[] array;

      MathArray(double[] array) {

            this.array = array;

      }

      void applyFunction(UnaryFunction uf) {
            int i;
            for(i = 0; i < array.length; i++) {
                  array[i] = uf.f(array[i]);
            }
      }

      void warnNaN(double d) {

            if(((Double)d).isNaN())
                  System.err.println("Warning: result is undefined");

      }

      void print() {

            for(int i = 0; i < array.length; i++)
                  System.out.print(array[i] + (i < array.length-1?", ":"\n"));

      }

}

public class Test {

      public static void main(String[] args) {

            MathArray te = new MathArray(new double[] { 0.1, 2.23, 3.08 });

            te.applyFunction(new SinUnary());

            te.print();
      }

}

05.07.2008 at 03:49PM PDT, ID: 21521026

perdoname_:

Actually i want for all the functors
But doing so eclipse returns error on test class

Any suggestions?

Please refer to code!

Thanks

                       
                          
                             
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                                interface UnaryFunction {
	public double f(double input);
}
 
class SinUnary implements UnaryFunction {
	public double f(double in) {
		return Math.sin(in);
	}
}
 
class CosUnary implements UnaryFunction {
	public double f(double in) {
		return Math.cos(in);
	}
}
 
class SqrtUnary implements UnaryFunction {
	public double f(double in) {
		return Math.sin(in);
	}
}
 
 
 
class MathArray {
 
	double[] array;
 
	MathArray(double[] array) {
 
		this.array = array;
 
	}
 
 
 
	void applyFunction(UnaryFunction uf) {
		int i;
		for(i = 0; i < array.length; i++) {
			array[i] = uf.f(array[i]);
		}
	}
 
	void warnNaN(double d) {
 
		if(((Double)d).isNaN())
			System.err.println("Warning: result is undefined");
 
	}
 
 
	void print() {
 
		for(int i = 0; i < array.length; i++)
			System.out.print(array[i] + (i < array.length-1?", ":"\n"));
 
	}
 
}
 
 
public class Test {
 
	public static void main(String[] args) {
 
		MathArray te = new MathArray(new double[] { 0.1, 2.23, 3.08 });
 
		te.applyFunction(new SinUnary(), new CosUnary(), new SqrtUnary());
 
		te.print();
	}
 
}

                             
                          

                    

Open in New Window

05.07.2008 at 03:52PM PDT, ID: 21521050

Rank: Genius

objects:

> te.applyFunction(new SinUnary(), new CosUnary(), new SqrtUnary());

should be:
te.applyFunction(new SinUnary());
te.applyFunction(new CosUnary());
te.applyFunction(new SqrtUnary());

05.07.2008 at 04:20PM PDT, ID: 21521209

perdoname_:

So will the code actually implements functors in that way ?

                       
                          
                             
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                                interface UnaryFunction {
	public double f(double input);
}
 
class SinUnary implements UnaryFunction {
	public double f(double in) {
		return Math.sin(in);
	}
}
 
class CosUnary implements UnaryFunction {
	public double f(double in) {
		return Math.cos(in);
	}
}
 
class SqrtUnary implements UnaryFunction {
	public double f(double in) {
		return Math.sin(in);
	}
}
 
 
 
class MathArray {
 
	double[] array;
 
	MathArray(double[] array) {
 
		this.array = array;
 
	}
 
 
 
	void applyFunction(UnaryFunction uf) {
		int i;
		for(i = 0; i < array.length; i++) {
			array[i] = uf.f(array[i]);
		}
	}
 
	void warnNaN(double d) {
 
		if(((Double)d).isNaN())
			System.err.println("Warning: result is undefined");
 
	}
 
 
	void print() {
 
		for(int i = 0; i < array.length; i++)
			System.out.print(array[i] + (i < array.length-1?", ":"\n"));
 
	}
 
}
 
 
public class Test {
 
	public static void main(String[] args) {
 
		MathArray te = new MathArray(new double[] { 0.1, 2.23, 3.08 });
 
		te.applyFunction(new SinUnary());
		te.applyFunction(new CosUnary());
		te.applyFunction(new SqrtUnary());
 
		te.print();
	}
 
}

                             
                          

                    

Open in New Window

05.07.2008 at 04:33PM PDT, ID: 21521257

Rank: Genius

objects:

that will result in each function being applied to the array

05.07.2008 at 05:20PM PDT, ID: 21521433

perdoname_:

I mean about the general program does it actually implement the functors?

05.07.2008 at 05:22PM PDT, ID: 21521445

Rank: Genius

objects:

The CosUnary, SinUnary and SqrtUnary classes implement the UnaryFunction

05.07.2008 at 05:24PM PDT, ID: 21521454

perdoname_:

Actually thats what the original code looks like and the point was to be modified as to implement the functors

                       
                          
                             
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                                class MathArray { 
 
	double[] array; 
 
	MathArray(double[] array) { 
 
		this.array = array; 
 
	} 
 
	void warnNaN(double d) { 
 
		if(((Double)d).isNaN()) 
			System.err.println("Warning: result is undefined"); 
 
	} 
 
 
 
	void applyNeg() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = -array[i]; 
 
			warnNaN(array[i]); 
 
		} 
	} 
 
	void applySqrt() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.sqrt(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void applySin() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.sin(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void applyCos() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.cos(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void print() { 
 
		for(int i = 0; i < array.length; i++) 
			System.out.print(array[i] + (i < array.length-1?", ":"\n")); 
 
	} 
 
} 
 
 
public class Test { 
 
	public static void main(String[] args) { 
 
		MathArray te = new MathArray(new double[] {0.1, 2.23, 3.08}); 
 
		// apply -Sqrt(Sin(x)) to each element x in the array: 
 
		te.applySin(); 
 
		te.applySqrt(); 
 
		te.applyNeg(); 
 
		te.print(); 
 
	} 
}
                             
                          

                    

Open in New Window

05.07.2008 at 05:28PM PDT, ID: 21521473

perdoname_:

Is it possible to be modified i mean in the same way with the single method as in the other code but to work with the current functors?

05.07.2008 at 05:30PM PDT, ID: 21521484

Rank: Genius

objects:

not sure i follow, what functors are you referring to
this method already works with your functors

void applyFunction(UnaryFunction uf) {
...

05.07.2008 at 05:33PM PDT, ID: 21521495

perdoname_:

I mean to work with those functors:

void applySqrt() {
            for(int i = 0; i < array.length; i++) {
                  array[i] = Math.sqrt(array[i]);
                  warnNaN(array[i]);
            }
      }

      void applySin() {
            for(int i = 0; i < array.length; i++) {
                  array[i] = Math.sin(array[i]);
                  warnNaN(array[i]);
            }
      }

      void applyCos() {
            for(int i = 0; i < array.length; i++) {
                  array[i] = Math.cos(array[i]);
                  warnNaN(array[i]);
            }
      }

And the applyFunction() to take as a parameter a functor and then to apply it on array

Any suggestions?

05.07.2008 at 05:38PM PDT, ID: 21521515

Rank: Genius

objects:

thats what the applyFunction alreasdy does, u can get rid of those 3 methods

05.07.2008 at 05:48PM PDT, ID: 21521556

perdoname_:

So in case of modifying the original code would the result be the same ?
or is there any other alternative way ?

05.07.2008 at 05:51PM PDT, ID: 21521572

Rank: Genius

objects:

what original code are u referring to?

05.07.2008 at 05:52PM PDT, ID: 21521576

perdoname_:

To that one:

                       
                          
                             
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                                class MathArray { 
 
	double[] array; 
 
	MathArray(double[] array) { 
 
		this.array = array; 
 
	} 
 
	void warnNaN(double d) { 
 
		if(((Double)d).isNaN()) 
			System.err.println("Warning: result is undefined"); 
 
	} 
 
 
 
	void applyNeg() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = -array[i]; 
 
			warnNaN(array[i]); 
 
		} 
	} 
 
	void applySqrt() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.sqrt(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void applySin() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.sin(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void applyCos() { 
 
		for(int i = 0; i < array.length; i++) { 
 
			array[i] = Math.cos(array[i]); 
 
			warnNaN(array[i]); 
 
		} 
 
	} 
 
	void print() { 
 
		for(int i = 0; i < array.length; i++) 
			System.out.print(array[i] + (i < array.length-1?", ":"\n")); 
 
	} 
 
} 
 
 
public class Test { 
 
	public static void main(String[] args) { 
 
		MathArray te = new MathArray(new double[] {0.1, 2.23, 3.08}); 
 
		// apply -Sqrt(Sin(x)) to each element x in the array: 
 
		te.applySin(); 
 
		te.applySqrt(); 
 
		te.applyNeg(); 
 
		te.print(); 
 
	} 
}

                             
                          

                    

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05.07.2008 at 05:58PM PDT, ID: 21521598

Rank: Genius

objects:

Implementing it as I showed in my first comment would seem the way to go.
If you want to be able to pass two functors it would be:

void applyFunctions(UnaryFunction uf1, UnaryFunction uf2) {
int i;
for(i = 0; i < array.length; i++) {
array[i] = uf1.f(uf2.f(array[i]));
}
}

Accepted Solution

20080236-EE-VQP-29 / EE_QW_2_20070628