Updated examples/cpque.c to better explain the i_less_functor template parameter.

1 files changed, 25 insertions, 26 deletions

diff --git a/examples/cpque.c b/examples/cpque.c
index 502a8c7b..63d07c6b 100644
--- a/examples/cpque.c
+++ b/examples/cpque.c
@@ -1,5 +1,9 @@
 // Implements c++ example: https://en.cppreference.com/w/cpp/container/priority_queue
-// Example of dynamic compare function
+// Example of per-instance less-function on a single priority queue type
+//
+// Note: i_less_functor: available for cpque types
+//       i_cmp_functor: available for csmap and csset types
+//       i_hash_functor/i_eq_functor: available for cmap and cset types
 
 #include <stdio.h>
 #include <stdbool.h>
@@ -14,9 +18,11 @@ struct {
     bool (*less)(const int*, const int*);
 } typedef IPQueue;
 
+#define IPQueue_obj(less) ((IPQueue){ipque_init(), less})
+
 #define i_type ipque
 #define i_val int
-#define i_opt c_declared // avoid redeclaring container type
+#define i_opt c_declared // needed to avoid re-type-define container type
 #define i_less_functor(self, x, y) c_container_of(self, IPQueue, Q)->less(x, y) // <== This.
 #include <stc/cpque.h>
 
@@ -27,7 +33,7 @@ struct {
 } while(0)
 
 void print_queue(const char* name, IPQueue q) {
-    // NB: make a copy because there is no way to traverse
+    // NB: make a clone because there is no way to traverse
     // priority_queue's content without erasing the queue.
     IPQueue copy = {ipque_clone(q.Q), q.less};
     
@@ -46,27 +52,20 @@ int main()
     const int data[] = {1,8,5,6,3,4,0,9,7,2}, n = c_arraylen(data);
     print("data", data, n);
 
-    IPQueue q1 = {ipque_init(), int_less};  // Max priority queue
-
-    c_forrange (i, n)
-        ipque_push(&q1.Q, data[i]);
-
-    print_queue("q1", q1);
-
-    // Min priority queue
-    // std::greater<int> makes the max priority queue act as a min priority queue
-    IPQueue minq1 = {ipque_init(), int_greater};
-    c_forrange (i, n) ipque_push(&minq1.Q, data[i]);
-
-    print_queue("minq1", minq1);
-
-    // Using lambda to compare elements.
-    IPQueue q5 = {ipque_init(), int_lambda};
-
-    c_forrange (i, n)
-        ipque_push(&q5.Q, data[i]);
-    
-    print_queue("q5", q5);
-
-    c_drop(ipque, &q1.Q, &minq1.Q, &q5.Q);
+    c_with (IPQueue q1 = IPQueue_obj(int_less), ipque_drop(&q1.Q))   // Max priority queue
+    c_with (IPQueue minq1 = IPQueue_obj(int_greater), ipque_drop(&minq1.Q)) // Min priority queue
+    c_with (IPQueue q5 = IPQueue_obj(int_lambda), ipque_drop(&q5.Q)) // Using lambda to compare elements.
+    {
+        c_forrange (i, n)
+            ipque_push(&q1.Q, data[i]);
+        print_queue("q1", q1);
+
+        c_forrange (i, n)
+            ipque_push(&minq1.Q, data[i]);
+        print_queue("minq1", minq1);
+
+        c_forrange (i, n)
+            ipque_push(&q5.Q, data[i]);
+        print_queue("q5", q5);
+    }
 }