From bb8484be936d82f0f01b99ca67a6de1508037e8f Mon Sep 17 00:00:00 2001
From: Tyge Løvset <tylo@norceresearch.no>
Date: Thu, 19 May 2022 11:22:03 +0200
Subject: Added _toval() in carc and cbox. Added dynamic polymorphism example,
 shape.c.

---
 examples/shape.c | 134 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 examples/shape.c

(limited to 'examples/shape.c')

diff --git a/examples/shape.c b/examples/shape.c
new file mode 100644
index 00000000..7dc52759
--- /dev/null
+++ b/examples/shape.c
@@ -0,0 +1,134 @@
+// Demo of typesafe polymorphism in C99, using STC.
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <stc/ccommon.h>
+
+#define c_self(s, T, vtable) \
+    T* self = c_container_of(s, T, vtable)
+#define c_is_first(T, memb) \
+    c_static_assert(offsetof(T, memb) == 0)
+
+
+typedef struct { float x, y; } Point;
+
+typedef struct Shape {
+    void (*drop)(struct Shape**);
+    void (*draw)(struct Shape**);
+} Shape;
+
+void Shape_drop(Shape** shape)
+{
+}
+
+void Shape_delete(Shape** shape)
+{ 
+    if (shape) {
+        (*shape)->drop(shape);
+        c_free(shape);
+    }
+}
+
+// Triangle implementation
+// ============================================================
+
+typedef struct {
+    Shape* api;
+    Point p[3];
+} Triangle;
+
+c_is_first(Triangle, api);
+
+
+void Triangle_draw(Shape** shape)
+{
+    const c_self(shape, Triangle, api);
+    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 Shape Triangle_api = {
+    .drop = Shape_drop,
+    .draw = Triangle_draw,
+};
+
+Shape** Triangle_new(Point a, Point b, Point c)
+{
+    Triangle* s = c_new(Triangle, {&Triangle_api, .p={a, b, c}});
+    return &s->api;
+}
+
+// Polygon implementation
+// ============================================================
+
+#define i_type PVec 
+#define i_val Point
+#include <stc/cstack.h>
+
+typedef struct {
+    Shape* api;
+    PVec points;
+} Polygon;
+
+c_is_first(Polygon, api);
+
+
+void Polygon_drop(Shape** shape)
+{
+    puts("drop poly");
+    c_self(shape, Polygon, api);
+    PVec_drop(&self->points);
+}
+
+void Polygon_draw(Shape** shape)
+{
+    const c_self(shape, Polygon, api);
+    printf("Polygon:");
+    c_foreach (i, PVec, self->points)
+        printf(" (%g,%g)", i.ref->x, i.ref->y);
+    puts("");
+}
+
+static Shape Polygon_api = {
+    .drop = Polygon_drop,
+    .draw = Polygon_draw,
+};
+
+Shape** Polygon_new(void)
+{
+    Polygon* s = c_new(Polygon, {&Polygon_api, .points=PVec_init()});
+    return &s->api;
+}
+
+void Polygon_addPoint(Shape** shape, Point p)
+{
+    c_self(shape, Polygon, api);
+    PVec_push(&self->points, p);
+}
+
+
+// Test
+// ============================================================
+
+void testShape(Shape** shape)
+{
+    (*shape)->draw(shape);
+}
+
+int main(void)
+{
+    c_autovar (Shape** tria = NULL, Shape_delete(tria))
+    c_autovar (Shape** poly = Polygon_new(), Shape_delete(poly))
+    {
+        tria = Triangle_new((Point){5, 7}, (Point){12, 7}, (Point){12, 20});
+
+        c_apply(p, Polygon_addPoint(poly, p), Point, {
+            {5, 7}, {12, 7}, {12, 20}, {82, 33}, {17, 56},
+        });
+
+        testShape(tria);
+        testShape(poly);
+    }
+}
-- 
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