minor tweaks

Author: fsaadatmand

chapter06/6-5.c

@@ -1,6 +1,7 @@
 /*
  * Exercise 6-5. Write a function undef that will remove a name and a
  * definition from the table maintained by lookup and install.
+ *
  * By Faisal Saadatmand
  */
 
@@ -18,7 +19,7 @@ struct nlist {                         /* table entry: */
 
 /* functions */
 unsigned hash(char *);
-char *strDup(char *);
+//char *strDup(char *);
 struct nlist *lookup(char *);
 struct nlist *install(char *, char *);
 void undef(char *);
@@ -33,8 +34,8 @@ char *strDup(char *s)
 {
 	char *p;
 
-	p = (char *) malloc(strlen(s) + 1); /* +1 for '\0' */
-	if (p != NULL)
+	p = malloc(strlen(s) + 1); /* +1 for '\0' */
+	if (p)
 		strcpy(p, s);
 	return p;
 }
@@ -44,7 +45,7 @@ unsigned hash(char *s)
 {
 	unsigned hashval;
 
-	for (hashval = 0; *s != '\0'; s++)
+	for (hashval = 0; *s; s++)
 		hashval = *s + (31 * hashval);
 	return hashval % HASHSIZE;
 }
@@ -54,8 +55,8 @@ struct nlist *lookup(char *s)
 {
 	struct nlist *np;
 
-	for (np = hashtab[hash(s)]; np != NULL; np = np->next)
-		if (strcmp(s, np->name) == 0)
+	for (np = hashtab[hash(s)]; np; np = np->next)
+		if (!strcmp(s, np->name))
 			return np;                 /* found */
 	return NULL;
 }
@@ -66,9 +67,9 @@ struct nlist *install(char *name, char *defn)
 	struct nlist *np;
 	unsigned hashval;
 
-	if ((np = lookup(name)) == NULL) { /* not found */
-		np = (struct nlist *) malloc(sizeof(*np));
-		if (np == NULL || (np->name = strDup(name)) == NULL)
+	if (!(np = lookup(name))) { /* not found */
+		np = malloc(sizeof(*np));
+		if (!np || !(np->name = strDup(name)))
 			return NULL;               /* no (heap) memory */
 		hashval = hash(name);
 		np->next = hashtab[hashval];
@@ -78,7 +79,7 @@ struct nlist *install(char *name, char *defn)
 
 	np->defn = strDup(defn);           /* copy definition */
 
-	if (np->defn == NULL)
+	if (!np->defn)
 		return NULL;
 	return np;
 }
@@ -88,7 +89,7 @@ void undef(char *s)
 {
 	struct nlist *np;
 
-	if ((np = lookup(s)) != NULL) {
+	if ((np = lookup(s))) {
 		free((void *) np->name);       /* free name memory */
 		free((void *) np->defn);       /* free definition memory */
 		hashtab[hash(s)] = np->next;   /* clear index or relink next node */
@@ -100,19 +101,18 @@ void undef(char *s)
 void printtab(struct nlist *node[], int size)
 {
 	int i;
-	for (i = 0; i < size; i++)
-		if (node[i] != NULL)
-			printf("%i  name: %s  defn: %s\n",
-					i, node[i]->name, node[i]->defn);
+	for (i = 0; i < size; ++i)
+		if (node[i])
+			printf("%i  name: %s  defn: %s\n", i, node[i]->name, node[i]->defn);
 }
 
 /* freetable: free table's (and its content's) allocated memory from heap */
 void freetable(struct nlist *node[], int size)
 {
 	int i;
 
-	for (i = 0; i < size; i++)
-		if (node[i] != NULL) {
+	for (i = 0; i < size; ++i)
+		if (node[i]) {
 			free(node[i]->name);
 			free(node[i]->defn);
 			free(node[i]);
@@ -126,17 +126,13 @@ int main(void)
 	/* insert nodes (skipped error checking) */
 	p = install("YES", "1");
 	p = install("NO", "0"); 
-
 	printf("Hash Table Values:\n");
 	printtab(hashtab, HASHSIZE);
-
 	/* delete a node */
 	printf("\nDelete \"YES\"\n\n");
 	undef("YES");
-
 	printf("Hash Table Values (After Deletion):\n");
 	printtab(hashtab, HASHSIZE);
-
 	freetable(hashtab, HASHSIZE);      /* clean up */
 	return 0;
 }