Second update on iterators - DEQUE

examples/deque/README.md

@@ -1,3 +1,4 @@
 # Deque examples
 
 * even_odd.c - separates odd numbers to one end of the deque and even number to the other. Sum only half of it to give the total sum of even numbers.
+* iterator.c - A complete example of the deque iterator

examples/deque/iterator.c

@@ -0,0 +1,199 @@
+/**
+ * iterator.c
+ *
+ * Creation Date: 13/05/2019
+ *
+ * Authors:
+ * Leonardo Vencovsky (https://github.com/LeoVen)
+ *
+ * Iterator Example
+ */
+#include "deque.h"
+#include <stdio.h>
+#include <inttypes.h>
+
+// Creates a deque of integers
+DEQUE_GENERATE(d, deque, /* FMOD */, int)
+
+int main(int argc, char const *argv[])
+{
+    // Create a new deque with an initial capacity of 100
+    deque *my_deque = d_new(100);
+
+    // Add elements to the deque
+    for (int i = 0; i < 20; i++)
+    {
+        // Add odd numbers to the front
+        d_push_front_if(my_deque, i, !(i % 2 == 0));
+
+        // And even numbers to the back
+        d_push_back_if(my_deque, i, i % 2 == 0);
+    }
+
+    // Iterate from the start (index 0) to the end (index count - 1) of the deque
+    for (deque_iter it = my_deque->it_start(my_deque); // Initialize iterator 'it' to the start of the deque
+         !d_iter_end(&it);                             // Conditional stop (until it is not at the end)
+         d_iter_next(&it))                             // Iterator goes one position forward
+    {
+        // Access the current element
+        int e = d_iter_value(&it);
+
+        // Access the current index (index is relative to all the elements in the iteration)
+        size_t i = d_iter_index(&it);
+
+        // Print deque
+
+        // 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 == d_count(my_deque) - 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 = d_count(my_deque) / 2;
+    for (deque_iter it = my_deque->it_start(my_deque); !d_iter_end(&it); d_iter_next(&it))
+    {
+        // Access the current element
+        int e = d_iter_value(&it);
+
+        // Access the current index (index is relative to all the elements in the iteration)
+        size_t i = d_iter_index(&it);
+
+        // Print deque 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 deque
+        {
+            printf("%d ]\n", e);
+            break;
+        }
+        // For elements at the middle
+        else
+            printf("%d, ", e);
+    }
+
+    // Going backwards
+    for (deque_iter it = my_deque->it_end(my_deque); // Initialize iterator 'it' to the end of the deque
+         !d_iter_start(&it);                         // Conditional stop (until it is not at the start)
+         d_iter_prev(&it))                           // Iterator goes one position backwards
+    {
+        // Access the current element
+        int e = d_iter_value(&it);
+
+        // Access the current index (index is relative to all the elements in the iteration)
+        size_t i = d_iter_index(&it);
+
+        // Print deque
+        // 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 == d_count(my_deque) - 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
+    deque_iter it;
+
+    // You have three options:
+    // - Initialize it using the functions provided by the deque [ my_deque->it_start() and my_deque->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_deque->it_start(my_deque);
+    it = my_deque->it_end(my_deque);
+
+    // This is equivalent to it_start()
+    d_iter_init(&it, my_deque);
+
+    // For pointers
+    // Also equivalent to it_start()
+    deque_iter *iter = d_iter_new(my_deque);
+
+    // The actual while loop
+    while (!d_iter_end(iter))
+    {
+        // Accessing elements
+        int e = d_iter_value(iter);
+        size_t i = d_iter_index(iter);
+
+        // Print index and element
+        printf("deque[%2" PRIuMAX "] = %2d\n", i, e);
+
+        // Move iterator forwards
+        d_iter_next(iter);
+    }
+
+    // Send the iterator to the start of the deque
+    d_iter_to_start(iter);
+
+    // Send the iterator to the end of the deque
+    d_iter_to_end(iter);
+
+    // Backwards loop
+    while (!d_iter_start(iter))
+    {
+        // Accessing elements
+        int e = d_iter_value(iter);
+        size_t i = d_iter_index(iter);
+
+        // Print index and element
+        printf("deque[%2" PRIuMAX "] = %2d\n", i, e);
+
+        // Move iterator backwards
+        d_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
+
+    // Change every element that is divisible by 3 to the number 7
+    for (d_iter_to_start(&it); !d_iter_end(&it); d_iter_next(&it))
+    {
+        // Get a reference to the current value
+        int *r = d_iter_rvalue(&it);
+
+        if (r != NULL && *r % 3 == 0)
+            *r = 7;
+    }
+
+    // Now print it to see the difference
+    for (deque_iter it = my_deque->it_start(my_deque); !d_iter_end(&it); d_iter_next(&it))
+    {
+        int e = d_iter_value(&it);
+        size_t i = d_iter_index(&it);
+
+        if (i == 0)
+            printf("[ %d, ", e);
+        else if (i == d_count(my_deque) - 1)
+            printf("%d ]\n", e);
+        else
+            printf("%d, ", e);
+    }
+
+    // Dispose the iterator called by d_iter_new()
+    d_iter_free(iter);
+    // Dispose the deque created
+    d_free(my_deque);
+
+    return 0;
+}

examples/iterators/deque.c

@@ -32,26 +32,30 @@ int main(int argc, char const *argv[])
     // Make the iterator go back and forward
     for (int j = 0; j < 4; j++)
     {
-        while (d_iter_next(&iter, &r, &i))
-            printf("C[%2d] = %2d\n", i, r);
+        while (!d_iter_end(&iter))
+        {
+            printf("C[%2d] = %2d\n", d_iter_index(&iter), d_iter_value(&iter));
+            d_iter_next(&iter);
+        }
         printf("\n");
-        while (d_iter_prev(&iter, &r, &i))
-            printf("C[%2d] = %2d\n", i, r);
+        while (!d_iter_start(&iter))
+        {
+            printf("C[%2d] = %2d\n", d_iter_index(&iter), d_iter_value(&iter));
+            d_iter_prev(&iter);
+        }
         printf("\n\n");
     }
 
-    for (d_iter_tostart(&iter); !d_iter_end(&iter); /**/)
+    for (d_iter_to_start(&iter); !d_iter_end(&iter); d_iter_next(&iter))
     {
-        d_iter_next(&iter, &r, &i);
-        printf("D[%2d] = %2d\n", i, r);
+        printf("D[%2d] = %2d\n", d_iter_index(&iter), d_iter_value(&iter));
     }
 
     printf("\n");
 
-    for (d_iter_toend(&iter); !d_iter_start(&iter); /**/)
+    for (d_iter_to_end(&iter); !d_iter_start(&iter); d_iter_prev(&iter))
     {
-        d_iter_prev(&iter, &r, &i);
-        printf("D[%2d] = %2d\n", i, r);
+        printf("D[%2d] = %2d\n", d_iter_index(&iter), d_iter_value(&iter));
     }
 
     d_free(d);

examples/list/iterator.c

@@ -67,7 +67,7 @@ int main(int argc, char const *argv[])
         if (i == 0)
             printf("[ %d, ", e);
         // If it is the last element
-        else if (i == limit)
+        else if (i == limit - 1) // -1 because index is 0 based and we want half of the list
         {
             printf("%d ]\n", e);
             break;