Tenth update on iterators - TREESET

examples/treeset/README.md

@@ -1,4 +1,5 @@
 # Treeset examples
 
+* iterator.c - A complete example of the treeset iterator
 * set_ops.c - Demonstrates common set operations like *union*, *intersection*, *difference* and *symmetric difference*.
 * tree_print.c - How to print a binary tree.

examples/treeset/iterator.c

@@ -0,0 +1,194 @@
+/**
+ * iterator.c
+ *
+ * Creation Date: 16/05/2019
+ *
+ * Authors:
+ * Leonardo Vencovsky (https://github.com/LeoVen)
+ *
+ * Iterator Example
+ */
+#include "treeset.h"
+#include <stdio.h>
+#include <inttypes.h>
+
+// Int hash function
+size_t inthash(int t)
+{
+    size_t a = t;
+    a += ~(a << 15);
+    a ^= (a >> 10);
+    a += (a << 3);
+    a ^= (a >> 6);
+    a += ~(a << 11);
+    a ^= (a >> 16);
+    return a;
+}
+
+// Int compare function
+int intcmp(int a, int b)
+{
+    return a - b;
+}
+
+// Creates a treeset of integers
+TREESET_GENERATE(ts, treeset, /* FMOD */, int)
+
+int main(int argc, char const *argv[])
+{
+    // Create a new treeset with an initial capacity of 100 and load factor of 0.6
+    treeset *my_treeset = ts_new(intcmp);
+
+    // Add elements to the treeset
+    for (int i = 0; i < 20; i++)
+    {
+        ts_insert(my_treeset, i);
+    }
+
+    // Iterate from the start (index 0) to the end (index count - 1) of the treeset
+    for (treeset_iter it = my_treeset->it_start(my_treeset); // Initialize iterator 'it' to the start of the treeset
+         !ts_iter_end(&it);                                  // Conditional stop (until it is not at the end)
+         ts_iter_next(&it))                                  // Iterator goes one position forward
+    {
+        // Access the current element
+        int e = ts_iter_value(&it);
+
+        // Access the current index (index is relative to all the elements in the iteration)
+        size_t i = ts_iter_index(&it);
+
+        // Print treeset
+
+        // Index is useful in situations like this
+        // If it is the first element
+        if (i == 0)
+            printf("[ %d, ", e);
+        // If it is the last element
+        else if (i == ts_count(my_treeset) - 1)
+            printf("%d ]\n", e);
+        // For elements at the middle
+        else
+            printf("%d, ", e);
+    }
+
+    // Index can also be used to iterate over a certain portion of a collection
+    size_t limit = ts_count(my_treeset) / 2;
+    for (treeset_iter it = my_treeset->it_start(my_treeset); !ts_iter_end(&it); ts_iter_next(&it))
+    {
+        // Access the current element
+        int e = ts_iter_value(&it);
+
+        // Access the current index (index is relative to all the elements in the iteration)
+        size_t i = ts_iter_index(&it);
+
+        // Print treeset up until limit
+
+        // If it is the first element
+        if (i == 0)
+            printf("[ %d, ", e);
+        // If it is the last element
+        else if (i == limit - 1) // -1 because index is 0 based and we want half of the treeset
+        {
+            printf("%d ]\n", e);
+            break;
+        }
+        // For elements at the middle
+        else
+            printf("%d, ", e);
+    }
+
+    // Going backwards
+    for (treeset_iter it = my_treeset->it_end(my_treeset); // Initialize iterator 'it' to the end of the treeset
+         !ts_iter_start(&it);                              // Conditional stop (until it is not at the start)
+         ts_iter_prev(&it))                                // Iterator goes one position backwards
+    {
+        // Access the current element
+        int e = ts_iter_value(&it);
+
+        // Access the current index (index is relative to all the elements in the iteration)
+        size_t i = ts_iter_index(&it);
+
+        // Print treeset
+        // Note how the conditions for the first and last elements are simply swapped
+        // Because iterating backwards make the first element be the index count - 1
+        // and the last one be the index 0
+
+        // If it is the first element
+        if (i == ts_count(my_treeset) - 1)
+            printf("[ %d, ", e);
+        // If it is the last element
+        else if (i == 0)
+            printf("%d ]\n", e);
+        // For elements at the middle
+        else
+            printf("%d, ", e);
+    }
+
+    // You can also use iterators in a while loop
+    // But to do so you must declare the iterator struct outside the loop first
+    treeset_iter it;
+
+    // You have three options:
+    // - Initialize it using the functions provided by the treeset [ my_treeset->it_start() and my_treeset->it_end() ]
+    // - Initialize it using the init() function (when the iterator is already allocated)
+    // - Initialize it using the new() function (allocates on the heap, pointers only)
+
+    it = my_treeset->it_start(my_treeset);
+    it = my_treeset->it_end(my_treeset);
+
+    // This is equivalent to it_start()
+    ts_iter_init(&it, my_treeset);
+
+    // For pointers
+    // Also equivalent to it_start()
+    treeset_iter *iter = ts_iter_new(my_treeset);
+
+    // The actual while loop
+    while (!ts_iter_end(iter))
+    {
+        // Accessing elements
+        int e = ts_iter_value(iter);
+        size_t i = ts_iter_index(iter);
+
+        // Print index and element
+        printf("treeset[%2" PRIuMAX "] = %2d\n", i, e);
+
+        // Move iterator forwards
+        ts_iter_next(iter);
+    }
+
+    // Send the iterator to the start of the treeset
+    ts_iter_to_start(iter);
+
+    // Send the iterator to the end of the treeset
+    ts_iter_to_end(iter);
+
+    // Backwards loop
+    while (!ts_iter_start(iter))
+    {
+        // Accessing elements
+        int e = ts_iter_value(iter);
+        size_t i = ts_iter_index(iter);
+
+        // Print index and element
+        printf("treeset[%2" PRIuMAX "] = %2d\n", i, e);
+
+        // Move iterator backwards
+        ts_iter_prev(iter);
+    }
+
+    // Certain iterators also allow you to modify the contents it is iterating over
+    // Exceptions are collections that depend of the current state of the element
+    // like tree-based collections and heap (collections that have some kind of ordering).
+    // You also can't change the keys of an associative collection
+
+    // In the case of a treeset or any set, this is not possible because the
+    // values of a set are its keys. Changing the elements could cause the set
+    // to be in an invalid state.
+
+    // Dispose the iterator called by ts_iter_new()
+    ts_iter_free(iter);
+    // Dispose the treeset created
+    ts_free(my_treeset);
+
+    return 0;
+}

examples/treeset/set_ops.c

@@ -22,13 +22,13 @@ TREESET_GENERATE(set, set, /* static */, int)
 
 void print_set(set *s)
 {
-    size_t index;
-    int result;
     set_iter iter;
     set_iter_init(&iter, s);
-    for (set_iter_tostart(&iter); !set_iter_end(&iter);)
+    for (set_iter_to_start(&iter); !set_iter_end(&iter); set_iter_next(&iter))
     {
-        set_iter_next(&iter, &result, &index);
+        int result = set_iter_value(&iter);
+        size_t index = set_iter_index(&iter);
+
         if (index == 0)
             printf("[ %2d, ", result);
         else if (index == s->count - 1)

examples/treeset/tree_print.c

@@ -24,7 +24,7 @@ void print_tree(set_node *root, int height)
     for (int i = 0; i < height; i++)
         printf("|------- ");
 
-    printf("%d\n", root->key);
+    printf("%d\n", root->value);
 
     print_tree(root->left, height + 1);
 }