--- a/baum.c	Thu Feb 07 12:51:54 2008 +0100
+++ b/baum.c	Thu Feb 07 14:31:02 2008 +0100
@@ -9,18 +9,21 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-
+#include <string.h>
 
-struct Node {
-	char* name;
-	char value;
-	struct Node* down;
-	struct Node* right;
-};
+#include "baum.h"
+
+char action(struct Node* node);
 
 struct Node* root;
 
 
+void logit(char* text) {
+	fprintf(stderr, "[%s]\n", text);
+}
+
+
+/* new */
 struct Node* newNode(char* name) {
 	struct Node* node;
 	node = (struct Node*) malloc(sizeof(struct Node));
@@ -31,40 +34,105 @@
 	return node;
 }
 
-void init() {
-	root = newNode("print");
-	root->down = newNode("sum");
-}
 
-void cleanup(struct Node* node) {
+/* delete */
+void delete(struct Node* node) {
 	if (node->down != NULL) {
-		cleanup(node->down);
+		delete(node->down);
 	}
 	if (node->right != NULL) {
-		cleanup(node->right);
+		delete(node->right);
 	}
 	free(node); node=0;
 }
 
+
+/* print */
 void printNode(struct Node* node) {
 	printf("Node: %20s (%c)\n", node->name, node->value);
 }
 
 void printTree(struct Node* root) {
 	printNode(root);
+	printf("  down: ");
 	if (root->down != NULL) {
 		printTree(root->down);
+	} else {
+		printf("NULL\n");
 	}
+	printf("  right: ");
 	if (root->right != NULL) {
 		printTree(root->right);
+	} else {
+		printf("NULL\n");
 	}
 }
 
 
+char action_print(struct Node* node) {
+	printf("%c\n", action(node->down));
+	return 0;
+}
+
+char action_sum(struct Node* node) {
+	struct Node* tp;
+	tp = node->down;
+	while (tp != NULL) {
+		node->value += action(tp);
+		tp = tp->right;
+	}
+	return node->value;
+}
+
+char action_number(struct Node* node) {
+	return node->value;
+}
+
+char action(struct Node* node) {
+	if (strcmp(node->name, "print") == 0) {
+		logit("print-node");
+		return action_print(node);
+	} else if (strcmp(node->name, "sum") == 0) {
+		logit("sum-node");
+		return action_sum(node);
+	} else if (strcmp(node->name, "number") == 0) {
+		logit("number-node");
+		return action_number(node);
+	} else {
+		fprintf(stderr, "unknown kind of node");
+		exit(1);
+	}
+}
+
+
+
+/* traverse */
+void traverse(struct Node* root) {
+	/* each node controlls the nodes below itself */
+	action(root);
+}
+
+/* init */
+void init() {
+	root = newNode("print");
+	root->down = newNode("number");
+	root->down = newNode("sum");
+	root->down->down = newNode("number");
+	root->down->down->value = 70;  /* 'F' */
+	root->down->down->right = newNode("number");
+	root->down->down->right->value = 50;  /* '2' */
+	/* result should be 'x' */
+}
+
+
+/* main */
 int main(int argc, char* argv[]) {
 	init();
 	printTree(root);
-	cleanup(root);
+
+	action(root);
+
+	delete(root);
 	
 	return(0);
 }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/baum.h	Thu Feb 07 14:31:02 2008 +0100
@@ -0,0 +1,8 @@
+struct Node {
+	char* name;
+	char value;
+	struct Node* down;
+	struct Node* right;
+};
+
+