From e7e29d913e3e603e53713843b24cd8bf32e3ea30 Mon Sep 17 00:00:00 2001
From: Patrick Pelissier <Patrick.Pelissier@gmail.com>
Date: Sat, 1 Jun 2024 10:16:59 +0200
Subject: [PATCH] Add new example of variant

---
 example/ex11-variant01.c | 108 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 example/ex11-variant01.c

diff --git a/example/ex11-variant01.c b/example/ex11-variant01.c
new file mode 100644
index 00000000..82a9eb40
--- /dev/null
+++ b/example/ex11-variant01.c
@@ -0,0 +1,108 @@
+#include <stdio.h>
+#include "m-variant.h"
+#include "m-list.h"
+
+// Define the variant with the given basic types
+// A variant is an union of all its type, with the information needed to identify which type it holds
+VARIANT_DEF2(obj,
+             (boolean, bool, M_BOOL_OPLIST),
+             (integer,  int,  M_BASIC_OPLIST),
+             (real, double, M_BASIC_OPLIST),
+             (cstr, const char*, M_CSTR_OPLIST))
+// Associate obj_t to its oplist, so that we can only use 'obj_t'
+// and M*LIB knows how to handle this type properly
+// We need to extend the oplist with FIELD so that M*LIB is able to generate 'emplace' functions
+#define M_OPL_obj_t()                                                   \
+  VARIANT_OPLIST(obj, M_OPEXTEND(M_BOOL_OPLIST, FIELD(boolean)),        \
+                 M_OPEXTEND(M_BASIC_OPLIST, FIELD(integer)),            \
+                 M_OPEXTEND(M_BASIC_OPLIST, FIELD(real)),               \
+                 M_OPEXTEND(M_CSTR_OPLIST, FIELD(cstr)))
+
+// Define a list over the variant
+LIST_DEF(list, obj_t)
+// Associate list_t to its oplist, so that we can only use 'list_t'
+#define M_OPL_list_t() LIST_OPLIST(list, M_OPL_obj_t())
+
+/* Print the type of the object */
+static void print_obj(obj_t o, const char name[])
+{
+  if (obj_empty_p(o)) {
+    printf("Object %s is empty\n", name);
+  }
+  if (obj_boolean_p(o)) {
+    printf("Object %s is a boolean (%d)\n", name, *obj_get_boolean(o));
+  }
+  if (obj_integer_p(o)) {
+    printf("Object %s is an integer (%d)\n", name, *obj_get_integer(o));
+  }
+  if (obj_real_p(o)) {
+    printf("Object %s is a float (%f)\n", name, *obj_get_real(o));
+  }
+  if (obj_cstr_p(o)) {
+    printf("Object %s is C string (%s)\n", name, *obj_get_cstr(o));
+  }
+}
+
+
+static void f(void)
+{
+  // Initialize & afterward clear the object
+  M_LET(o, obj_t) {
+    print_obj(o, "1st init");
+    obj_set_real(o, 23.4);
+    print_obj(o, "1st+set");
+  } // Now the object is out of scope and is cleared.
+
+  // Initialize, set as an integer of value '12' & afterward clear the object
+  // () around 12 means that we want to 'emplace' object using the input '12' to construct the object in-place,
+  // rather than setting it from an already existing 'obj_t'.
+  // It checks for the type of 12, find it is an integer, and initalize o with this value
+  // It won't work if there is multiple compatible type in the variant
+  M_LET( (o, (12)), obj_t) {
+    print_obj(o, "2nd init");
+    obj_set_cstr(o, "Hello");
+    print_obj(o, "2nd+set");
+  }
+
+  M_LET( (o, (true)), obj_t) {
+    // In C11, a 'true' value is an 'int' type, not a bool!
+    print_obj(o, "3rd init");
+    obj_set_boolean(o, true);
+    print_obj(o, "3rd+set");
+    // Without "()" around the source, it will set the value using the object builtin copy.
+    M_LET( (p, o), obj_t) {
+      print_obj(o, "3rd+rec");
+      // We can also print the object directly:
+      printf("OBJ=");
+      obj_out_str(stdout, o);
+      printf("\n");
+    }
+  }
+}
+
+static void g(void)
+{
+  // Initialize a list of obj_t and clear it afterwards
+  M_LET(l, list_t){
+    // Let's emplace some type in the list
+    list_emplace_back_boolean(l, true);
+    list_emplace_back_integer(l, 12);
+    list_emplace_back_cstr(l, "World");
+    list_emplace_back_real(l, 17.42);
+    // We can iterate on the list
+    for M_EACH(item, l, list_t) {
+        print_obj(*item, "loop");
+    }
+    // We can also print the object directly:
+    printf("LIST=");
+    list_out_str(stdout, l);
+    printf("\n");
+  } // Clear & free the list
+}
+
+int main(void)
+{
+  f();
+  g();
+  exit(0);
+}