Added possibility to have per container-instance customizable compare/lookup functions (cmp, less, eq, hash) for priority queue and associative containers. Is achived by embedding the container in a struct along with function pointer(s) which can be accessed through the c_container_of() macro. See the updated cpque.c example in the examples folder.

1 files changed, 52 insertions, 25 deletions

diff --git a/examples/cpque.c b/examples/cpque.c
index 5866f17b..502a8c7b 100644
--- a/examples/cpque.c
+++ b/examples/cpque.c
@@ -1,24 +1,40 @@
 // Implements c++ example: https://en.cppreference.com/w/cpp/container/priority_queue
+// Example of dynamic compare function
+
 #include <stdio.h>
 #include <stdbool.h>
+#include <stc/forward.h>
+#include <stc/views.h>
 
-// Example of dynamic compare function
+// predeclare
+declare_cpque(ipque, int);
 
-static bool (*less_fn)(const int* x, const int* y);
+struct {
+    ipque Q;
+    bool (*less)(const int*, const int*);
+} typedef IPQueue;
 
-#define i_val int
-#define i_less less_fn
 #define i_type ipque
+#define i_val int
+#define i_opt c_declared // avoid redeclaring container type
+#define i_less_functor(self, x, y) c_container_of(self, IPQueue, Q)->less(x, y) // <== This.
 #include <stc/cpque.h>
 
-void print_queue(ipque q) {
-    ipque copy = ipque_clone(q);
-    while (!ipque_empty(&copy)) {
-        printf("%d ", *ipque_top(&copy));
-        ipque_pop(&copy);
-    }
+#define print(name, q, n) do { \
+    printf("%s: \t", name); \
+    c_forrange (i, n) printf("%d ", q[i]); \
+    puts(""); \
+} while(0)
+
+void print_queue(const char* name, IPQueue q) {
+    // NB: make a copy because there is no way to traverse
+    // priority_queue's content without erasing the queue.
+    IPQueue copy = {ipque_clone(q.Q), q.less};
+    
+    for (printf("%s: \t", name); !ipque_empty(&copy.Q); ipque_pop(&copy.Q))
+        printf("%d ", *ipque_top(&copy.Q));
     puts("");
-    ipque_drop(&copy);
+    ipque_drop(&copy.Q);
 }
 
 static bool int_less(const int* x, const int* y) { return *x < *y; }
@@ -28,18 +44,29 @@ static bool int_lambda(const int* x, const int* y) { return (*x ^ 1) < (*y ^ 1);
 int main()
 {
     const int data[] = {1,8,5,6,3,4,0,9,7,2}, n = c_arraylen(data);
-    c_auto (ipque, q, q2, q3)  // init() and defered drop()
-    {
-        less_fn = int_less;
-        c_forrange (i, n) ipque_push(&q, data[i]);
-        print_queue(q);
-
-        less_fn = int_greater;
-        c_forrange (i, n) ipque_push(&q2, data[i]);
-        print_queue(q2);
-
-        less_fn = int_lambda;
-        c_forrange (i, n) ipque_push(&q3, data[i]);
-        print_queue(q3);
-    }
+    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);
 }