Update example

example/ex-algo04.c

@@ -7,28 +7,31 @@ ARRAY_DEF(vector_int, int)
 /* Register the oplist of this array of int globally */
 #define M_OPL_vector_int_t() ARRAY_OPLIST(vector_int)
 
-/* Set s (string_t) to the integer i */
-#define str_ui(s, i) string_printf(s, "%d", i)
-
 /* Concat two strings by insertion a '-' within them */
 #define str_cat(s1, s2) (string_cat_str(s1, "-"), string_cat(s1, s2))
 
 int main(void)
 {
-  // Let s be a string_t and initilize it.
+  // Let 's' be a string_t and initialize it.
   M_LET(s, string_t)
-    // Let v be a vector of integer and initialize it.
+    // Let 'v' be a vector of integer and initialize it.
     M_LET( (v, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10), vector_int_t) {
     int sum = 0, product = 0;
     
     // Compute the sum of theses integers.
+    // 'add' is a registered keyword, recognized by M*LIB to perform a sum.
     ALGO_REDUCE(sum, v, vector_int_t, add);
 
     // Compute the product of theses integers.
+    // 'mul' is a registered keyword, recognized by M*LIB to perform a product.
     ALGO_REDUCE(product, v, vector_int_t, mul);
 
-    /* Example of reduction with a transformation of the type from int to string_t */
-    ALGO_REDUCE( (s, string_t), v, vector_int_t, str_cat, str_ui);
+    /* Example of reduction with a transformation of the type from int to string_t
+       By default, the result ("s") should be of the same type as the base type
+       of the container. This is not the case here, we want to transform the
+       type. As such, we add the precision of the type 'string_t' to 's'.
+       The transformation from string to integer is done by string_set_si */
+    ALGO_REDUCE( (s, string_t), v, vector_int_t, str_cat, string_set_si);
 
     printf ("sum: %d\n"
             "product: %d\n"