Ninth update on iterators - TREEMAP

examples/treemap/README.md

@@ -1,3 +1,4 @@
 # Treemap examples
 
 * pseudo_multiset.c - An example of how to make a multiset using a map.
+* iterator.c - A complete example of the treemap iterator

examples/treemap/iterator.c

@@ -0,0 +1,217 @@
+/**
+ * iterator.c
+ *
+ * Creation Date: 16/05/2019
+ *
+ * Authors:
+ * Leonardo Vencovsky (https://github.com/LeoVen)
+ *
+ * Iterator Example
+ */
+#include "treemap.h"
+#include <stdio.h>
+#include <inttypes.h>
+
+// Int compare function
+int intcmp(int a, int b)
+{
+    return a - b;
+}
+
+// Creates a treemap of integers
+TREEMAP_GENERATE(tm, treemap, /* FMOD */, int, double)
+
+int main(int argc, char const *argv[])
+{
+    // Create a new treemap
+    treemap *my_map = tm_new(intcmp);
+
+    // Add pairs to the treemap
+    for (int i = 0; i < 20; i++)
+    {
+        // Map integers to doubles
+        tm_insert(my_map, i, (double)i / 10.0);
+    }
+
+    // Iterate from the start (left-most node) to the end (right-most node) of the treemap
+    for (treemap_iter it = my_map->it_start(my_map); // Initialize iterator 'it' to the start of the treemap
+         !tm_iter_end(&it);                          // Conditional stop (until it is not at the end)
+         tm_iter_next(&it))                          // Iterator goes one position forward
+    {
+        // Access the current key
+        int k = tm_iter_key(&it);
+
+        // Access the current value
+        double v = tm_iter_value(&it);
+
+        // Access the current index (index is relative to all the pairs in the iteration)
+        size_t i = tm_iter_index(&it);
+
+        // Print treemap
+
+        // Index is useful in situations like this
+        // If it is the first pair
+        if (i == 0)
+            printf("[ {%d:%.2lf}, ", k, v);
+        // If it is the last pair
+        else if (i == tm_count(my_map) - 1)
+            printf("{%d:%.2lf} ]\n", k, v);
+        // For pairs at the middle
+        else
+            printf("{%d:%.2lf}, ", k, v);
+    }
+
+    // Index can also be used to iterate over a certain portion of a collection
+    size_t limit = tm_count(my_map) / 2;
+    for (treemap_iter it = my_map->it_start(my_map); !tm_iter_end(&it); tm_iter_next(&it))
+    {
+        // Access the current key
+        int k = tm_iter_key(&it);
+
+        // Access the current value
+        double v = tm_iter_value(&it);
+
+        // Access the current index (index is relative to all the pairs in the iteration)
+        size_t i = tm_iter_index(&it);
+
+        // Print treemap up until limit
+
+        // If it is the first pair
+        if (i == 0)
+            printf("[ {%d:%.2lf}, ", k, v);
+        // If it is the last pair
+        else if (i == limit - 1) // -1 because index is 0 based and we want half of the treemap
+        {
+            printf("{%d:%.2lf} ]\n", k, v);
+            break;
+        }
+        // For pairs at the middle
+        else
+            printf("{%d:%.2lf}, ", k, v);
+    }
+
+    // Going backwards
+    for (treemap_iter it = my_map->it_end(my_map); // Initialize iterator 'it' to the end of the treemap
+         !tm_iter_start(&it);                      // Conditional stop (until it is not at the start)
+         tm_iter_prev(&it))                        // Iterator goes one position backwards
+    {
+        // Access the current key
+        int k = tm_iter_key(&it);
+
+        // Access the current value
+        double v = tm_iter_value(&it);
+
+        // Access the current index (index is relative to all the pairs in the iteration)
+        size_t i = tm_iter_index(&it);
+
+        // Print treemap
+        // Note how the conditions for the first and last pairs are simply swapped
+        // Because iterating backwards make the first pair be the index count - 1
+        // and the last one be the index 0
+
+        // If it is the first pair
+        if (i == tm_count(my_map) - 1)
+            printf("[ {%d:%.2lf}, ", k, v);
+        // If it is the last pair
+        else if (i == 0)
+            printf("{%d:%.2lf} ]\n", k, v);
+        // For pairs at the middle
+        else
+            printf("{%d:%.2lf}, ", k, v);
+    }
+
+    // You can also use iterators in a while loop
+    // But to do so you must declare the iterator struct outside the loop first
+    treemap_iter it;
+
+    // You have three options:
+    // - Initialize it using the functions provided by the treemap [ my_map->it_start() and my_map->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_map->it_start(my_map);
+    it = my_map->it_end(my_map);
+
+    // This is equivalent to it_start()
+    tm_iter_init(&it, my_map);
+
+    // For pointers
+    // Also equivalent to it_start()
+    treemap_iter *iter = tm_iter_new(my_map);
+
+    // The actual while loop
+    while (!tm_iter_end(iter))
+    {
+        // Accessing pairs
+        int k = tm_iter_key(iter);
+        double v = tm_iter_value(iter);
+        size_t i = tm_iter_index(iter);
+
+        // Print index and key value pair
+        printf("treemap[%2" PRIuMAX "] = { %2d : %.2lf }\n", i, k, v);
+
+        // Move iterator forwards
+        tm_iter_next(iter);
+    }
+
+    // Send the iterator to the start of the treemap
+    tm_iter_to_start(iter);
+
+    // Send the iterator to the end of the treemap
+    tm_iter_to_end(iter);
+
+    // Backwards loop
+    while (!tm_iter_start(iter))
+    {
+        // Accessing pairs
+        int k = tm_iter_key(iter);
+        double v = tm_iter_value(iter);
+        size_t i = tm_iter_index(iter);
+
+        // Print index and the key value pair
+        printf("treemap[%2" PRIuMAX "] = { %2d : %.2lf }\n", i, k, v);
+
+        // Move iterator backwards
+        tm_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 pair
+    // like tree-based collections and heap (collections that have some kind of ordering).
+    // You also can't change the keys of an associative collection
+
+    // Change every value where its key is divisible by 3 to the number 7
+    for (tm_iter_to_start(&it); !tm_iter_end(&it); tm_iter_next(&it))
+    {
+        // Get current key
+        int k = tm_iter_key(&it);
+
+        // Get a reference to the current value
+        double *v = tm_iter_rvalue(&it);
+
+        if (k % 3 == 0)
+            *v = 7;
+    }
+
+    // Now print it to see the difference
+    for (treemap_iter it = my_map->it_start(my_map); !tm_iter_end(&it); tm_iter_next(&it))
+    {
+        int k = tm_iter_key(&it);
+        double v = tm_iter_value(&it);
+        size_t i = tm_iter_index(&it);
+
+        if (i == 0)
+            printf("[ {%d:%.2lf}, ", k, v);
+        else if (i == tm_count(my_map) - 1)
+            printf("{%d:%.2lf} ]\n", k, v);
+        else
+            printf("{%d:%.2lf}, ", k, v);
+    }
+
+    // Dispose the iterator called by tm_iter_new()
+    tm_iter_free(iter);
+    // Dispose the treemap created
+    tm_free(my_map);
+
+    return 0;
+}

examples/treemap/pseudo_multiset.c

@@ -12,6 +12,7 @@
 
 #include "treemap.h"
 #include <stdio.h>
+#include <inttypes.h>
 
 // Mapping an integer by size_t which will represent the key's multiplicity
 // (key could be anything and multiplicity could be an integer, preferably
@@ -36,7 +37,7 @@ void print_tree(tmap_node *root, int height)
         printf("|------- ");
 
     // Key:Multiplicity
-    printf("%d:%llu\n", root->key, root->value);
+    printf("%d:%" PRIuMAX "\n", root->key, root->value);
 
     print_tree(root->left, height + 1);
 }
@@ -73,15 +74,10 @@ int main(int argc, char const *argv[])
     printf("\n---------- SUMMARY ----------\n\n");
 
     // Print using iterator
-    tmap_iter iter;
-    int key;
-    size_t mult, _;
-
-    for (tm_iter_init(&iter, map); !tm_iter_end(&iter); /* empty */)
+    for (tmap_iter it = map->it_start(map); !tm_iter_end(&it); tm_iter_next(&it))
     {
         // Map[key] = multiplicity
-        tm_iter_next(&iter, &key, &mult, &_);
-        printf("Map[%2d] = %llu\n", key, mult);
+        printf("Map[%2d] = %" PRIuMAX "\n", tm_iter_key(&it), tm_iter_value(&it));
     }
 
     tm_free(map);