Properly link flecs library

engine/libs/flecs/examples/c/entities/basics/src/main.c

@@ -0,0 +1,61 @@
+#include <basics.h>
+#include <stdio.h>
+
+typedef struct {
+    double x, y;
+} Position;
+
+int main(int argc, char *argv[]) {
+    ecs_world_t *ecs = ecs_init_w_args(argc, argv);
+
+    ECS_COMPONENT(ecs, Position);
+    ECS_TAG(ecs, Walking);
+
+    // Create an entity with name Bob
+    ecs_entity_t bob = ecs_set_name(ecs, 0, "Bob");
+
+    // The set operation finds or creates a component, and sets it.
+    ecs_set(ecs, bob, Position, {10, 20});
+    // The add operation adds a component without setting a value. This is
+    // useful for tags, or when adding a component with its default value.    
+    ecs_add(ecs, bob, Walking);
+
+    // Get the value for the Position component
+    const Position *ptr = ecs_get(ecs, bob, Position);
+    printf("{%f, %f}\n", ptr->x, ptr->y);
+
+    // Overwrite the value of the Position component
+    ecs_set(ecs, bob, Position, {20, 30});
+
+    // Create another named entity
+    ecs_entity_t alice = ecs_set_name(ecs, 0, "Alice");
+    ecs_set(ecs, alice, Position, {10, 20});
+    ecs_add(ecs, alice, Walking);
+
+    // Print all the components the entity has. This will output:
+    //    Position, Walking, (Identifier,Name)
+    char *str = ecs_type_str(ecs, ecs_get_type(ecs, alice));
+    printf("[%s]\n", str);
+    ecs_os_free(str);
+
+    // Remove tag
+    ecs_remove(ecs, alice, Walking);
+
+    // Iterate all entities with Position
+    ecs_iter_t it = ecs_term_iter(ecs, &(ecs_term_t){ .id = ecs_id(Position) });
+    while (ecs_term_next(&it)) {
+        Position *p = ecs_field(&it, Position, 1);
+        for (int i = 0; i < it.count; i ++) {
+            printf("%s: {%f, %f}\n", ecs_get_name(ecs, it.entities[i]),
+                p[i].x, p[i].y);
+        }
+    }
+
+    return ecs_fini(ecs);
+
+    // Output
+    //  {10.000000, 20.000000}
+    //  [Position, Walking, (Identifier,Name)]
+    //  Alice: {10.000000, 20.000000}
+    //  Bob: {20.000000, 30.000000}
+}