1 files changed, 159 insertions, 0 deletions
diff --git a/misc/examples/shape.c b/misc/examples/shape.c
new file mode 100644
index 00000000..a17208ef
--- /dev/null
+++ b/misc/examples/shape.c
@@ -0,0 +1,159 @@
+// Demo of typesafe polymorphism in C99, using STC.
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stc/ccommon.h>
+
+#define c_dyn_cast(T, s) \
+    (&T##_api == (s)->api ? (T*)(s) : (T*)0)
+
+// Shape definition
+// ============================================================
+
+typedef struct {
+    float x, y;
+} Point;
+
+typedef struct Shape Shape;
+
+struct ShapeAPI {
+    void (*drop)(Shape*);
+    void (*draw)(const Shape*);
+};
+
+struct Shape {
+    struct ShapeAPI* api;
+    uint32_t color;
+    uint16_t style;
+    uint8_t thickness;
+    uint8_t hardness;
+};
+
+void Shape_drop(Shape* shape)
+{
+    printf("shape destructed\n");
+}
+
+void Shape_delete(Shape* shape)
+{
+    if (shape) {
+        shape->api->drop(shape);
+        c_free(shape);
+    }
+}
+
+// Triangle implementation
+// ============================================================
+
+typedef struct {
+    Shape shape;
+    Point p[3];
+} Triangle;
+
+static struct ShapeAPI Triangle_api;
+
+
+Triangle Triangle_from(Point a, Point b, Point c)
+{
+    Triangle t = {{.api=&Triangle_api}, .p={a, b, c}};
+    return t;
+}
+
+static void Triangle_draw(const Shape* shape)
+{
+    const Triangle* self = c_dyn_cast(Triangle, shape);
+    printf("Triangle : (%g,%g), (%g,%g), (%g,%g)\n",
+           self->p[0].x, self->p[0].y,
+           self->p[1].x, self->p[1].y,
+           self->p[2].x, self->p[2].y);
+}
+
+static struct ShapeAPI Triangle_api = {
+    .drop = Shape_drop,
+    .draw = Triangle_draw,
+};
+
+// Polygon implementation
+// ============================================================
+
+#define i_type PointVec 
+#define i_val Point
+#include <stc/cstack.h>
+
+typedef struct {
+    Shape shape;
+    PointVec points;
+} Polygon;
+
+static struct ShapeAPI Polygon_api;
+
+
+Polygon Polygon_init(void)
+{
+    Polygon p = {{.api=&Polygon_api}, .points=PointVec_init()};
+    return p;
+}
+
+void Polygon_addPoint(Polygon* self, Point p)
+{
+    PointVec_push(&self->points, p);
+}
+
+static void Polygon_drop(Shape* shape)
+{
+    Polygon* self = c_dyn_cast(Polygon, shape);
+    printf("poly destructed\n");
+    PointVec_drop(&self->points);
+    Shape_drop(shape);
+}
+
+static void Polygon_draw(const Shape* shape)
+{
+    const Polygon* self = c_dyn_cast(Polygon, shape);
+    printf("Polygon  :");
+    c_foreach (i, PointVec, self->points)
+        printf(" (%g,%g)", i.ref->x, i.ref->y);
+    puts("");
+}
+
+static struct ShapeAPI Polygon_api = {
+    .drop = Polygon_drop,
+    .draw = Polygon_draw,
+};
+
+// Test
+// ============================================================
+
+#define i_type Shapes
+#define i_val Shape*
+#define i_valdrop(x) Shape_delete(*x)
+#include <stc/cstack.h>
+
+void testShape(const Shape* shape)
+{
+    shape->api->draw(shape);
+}
+
+
+int main(void)
+{
+    c_auto (Shapes, shapes)
+    {
+        Triangle* tri1 = c_new(Triangle, Triangle_from((Point){5, 7}, (Point){12, 7}, (Point){12, 20}));
+        Polygon* pol1 = c_new(Polygon, Polygon_init());
+        Polygon* pol2 = c_new(Polygon, Polygon_init());
+
+        c_forlist (i, Point, {{50, 72}, {123, 73}, {127, 201}, {828, 333}})
+            Polygon_addPoint(pol1, *i.ref);
+
+        c_forlist (i, Point, {{5, 7}, {12, 7}, {12, 20}, {82, 33}, {17, 56}})
+            Polygon_addPoint(pol2, *i.ref);
+        
+        Shapes_push(&shapes, &tri1->shape);
+        Shapes_push(&shapes, &pol1->shape);
+        Shapes_push(&shapes, &pol2->shape);
+
+        c_foreach (i, Shapes, shapes)
+            testShape(*i.ref);
+    }
+}