Transformation.java

package javaf.syb;

import javaf.prelude.*;

import java.lang.reflect.*;
import java.util.List;

public class Transformation {

    /**
     * Apply an action if possible.
     */
    public static <X> Action<Object> orIdentity(final Action<X> a) {
        return new Action<Object>() {
            
            @SuppressWarnings("unchecked")
            public void apply(Object x) {
                try { 
                    a.apply((X)x);
                }
                catch (ClassCastException _) {
                    // Do nothing
                }
            }
        };
    }

    /**
     * Apply a transformation to all immediate sub-objects.
     */
    public static Action<Object> all(final Action<Object> a) {
        return new Action<Object>() {
            @SuppressWarnings("rawtypes")
            public void apply(Object x) {
                // Special case for lists
                if (x instanceof List)
                    for (Object o : (List)x)
                        a.apply(o);
                else {
                    // Regular case based on getters
                    for (Method m : x.getClass().getDeclaredMethods()) {
                        if (m.getName().startsWith("get") 
                        && m.getParameterTypes().length == 0) {
                            try {
                                a.apply(m.invoke(x, new Object[]{}));
                            }
                            catch (IllegalAccessException e) {
                                // assert "DEAD CODE"
                            } catch (IllegalArgumentException e) {
                                // assert "DEAD CODE"
                            } catch (InvocationTargetException e) {
                                // assert "DEAD CODE"
                            }
                        }
                    }
                }
            }
        };
    }

    /**
     * Apply a function to each and every sub-object in bottom-up manner.
     */
    public static Action<Object> everywhere(final Action<Object> a) {        
        return new Action<Object>() {
            public void apply(Object x) {
                all(everywhere(a)).apply(x);
                a.apply(x);
            }
        };
    }
}