Properly link flecs library

engine/libs/flecs/examples/cpp/queries/iter/src/main.cpp

@@ -0,0 +1,65 @@
+#include <iter.h>
+#include <iostream>
+
+struct Position { 
+    double x, y;
+};
+
+struct Velocity { 
+    double x, y;
+};
+
+struct Mass {
+    double value;
+};
+
+int main(int, char *[]) {
+    flecs::world ecs;
+
+    // Create a query for Position, Velocity.
+    flecs::query<Position, const Velocity> q = 
+        ecs.query<Position, const Velocity>();
+
+    // Create a few test entities for a Position, Velocity query
+    ecs.entity("e1")
+        .set<Position>({10, 20})
+        .set<Velocity>({1, 2});
+
+    ecs.entity("e2")
+        .set<Position>({10, 20})
+        .set<Velocity>({3, 4});
+
+    ecs.entity("e3")
+        .set<Position>({10, 20})
+        .set<Velocity>({4, 5})
+        .set<Mass>({50});
+
+    // The iter function provides a flecs::iter object which contains all sorts
+    // of information on the entities currently being iterated.
+    // The function passed to iter is by default called for each table the query
+    // is matched with.
+    q.iter([&](flecs::iter& it, Position *p, const Velocity *v) {
+        // Print the table & number of entities matched in current callback
+        std::cout << "Table [" << it.type().str() << "]" << std::endl;
+        std::cout << " - number of entities: " << it.count() << std::endl;
+
+        // Print information about the components being matched
+        for (int i = 1; i <= it.field_count(); i ++) {
+            std::cout << " - term " << i << ": " << std::endl;
+            std::cout << "   - component: " << it.id(i).str() << std::endl;
+            std::cout << "   - type size: " << it.size(i) << std::endl;
+        }
+
+        std::cout << std::endl;
+
+        // Iterate entities
+        for (auto i : it) {
+            p[i].x += v[i].x;
+            p[i].y += v[i].y;
+            std::cout << " - " << it.entity(i).name() << 
+                ": {" << p[i].x << ", " << p[i].y << "}\n";
+        }
+
+        std::cout << std::endl;
+    });
+}