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example/ex11-algo02.c

@@ -17,10 +17,14 @@ ARRAY_DEF(vector_employee, employee_t)
 #define M_OPL_vector_employee_t() ARRAY_OPLIST(vector_employee, M_OPL_employee_t())
 ALGO_DEF(vector_employee, vector_employee_t)
 
-/* Define the function object to select the sort order */
+/* Define the function object to select the sort order
-FUNC_OBJ_INS_DEF(compare_by,
+ * named 'compare_by' which is an instance of the interface
-                 vector_employee_cmp_obj,
+ * 'vector_employee_cmp_obj' created by ALGO_DEF.
-                 (a, b), { 
+ */
+FUNC_OBJ_INS_DEF(compare_by /* name of the instance */,
+                 vector_employee_cmp_obj /* name of the interface */,
+                 (a, b) /* name of the input parameters of the function like object. The type are inherited from the interface. */, {
+                   /* code of the function object */
                    if (string_equal_str_p(self->sort_field, "name"))
                      return string_cmp(a->name, b->name);
                    else if (string_equal_str_p(self->sort_field, "age"))
@@ -28,6 +32,7 @@ FUNC_OBJ_INS_DEF(compare_by,
                    else
                      return a->idnum < b->idnum ? -1 : a->idnum > b->idnum;
                  },
+                 /* Additional fields stored in the function object */
                  (sort_field, string_t) )
 #define M_OPL_compare_by_t() FUNC_OBJ_INS_OPLIST(compare_by, STRING_OPLIST)
 
@@ -39,19 +44,25 @@ static void read(vector_employee_t base, const char filename[])
   // Open the file
   FILE *f = fopen(filename, "rt");
   if (!f) {
+    // Handle errors
     fprintf(stderr, "ERROR: Cannot open file '%s'.\n", filename);
     exit(2);
   }
+
   // Initialize the JSON serializer with this file
   M_LET( (in,f), m_serial_json_read_t)
+    // Read the JSON file and fill in 'base' with it.
     ret = vector_employee_in_serial(base, in);
-  // Let's handle errors
+
+  // Let's handle serialization error
   if (ret != M_SERIAL_OK_DONE) {
     fprintf(stderr, "ERROR: Cannot read JSON data from file '%s'.\nParsing stops at:\n", filename);
     while (!feof(f)) { fputc(fgetc(f), stdout); }
     fclose(f);
     exit(2);
   }
+
+  // Close the FILE
   fclose(f);
 }
 
@@ -67,11 +78,14 @@ int main(void)
     printf("Employees sorted by idnum are: ");
     vector_employee_out_str(stdout, emps);
 
+    // Sort the database by employee name
     M_LET( (cmp, STRING_CTE("name")), compare_by_t )
       vector_employee_sort_fo(emps, compare_by_as_interface(cmp));
     printf("\nEmployees sorted by name are: ");
     vector_employee_out_str(stdout, emps);
     printf("\n");
+
+    // End
   }
   return 0;
 }