Add support for given an argument for the initialization of a variable in M_LET

if the variable is within parenthesis:
 M_LET((a,b), string_t)
 ==> It will init a & set it to b.

For the moment, we can only init with value of the same type (through init_set)

m-core.h

@@ -507,6 +507,10 @@
 #define M_RETI_ARG53(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, _21, _22, _23, _24, _25, _26, _27, _28, _29, _30, _31, _32, _33, _34, _35, _36, _37, _38, _39, _40, _41, _42, _43, _44, _45, _46, _47, _48, _49, _50, _51, _52, _53, ...) _53
 #define M_RET_ARG53(...) M_RETI_ARG53(__VA_ARGS__)
 
+/* For a pair of argument (arg0, arg1), return either the first or the second.
+   Needed in case where M_RET_ARGn cannot be used */
+#define M_PAIR_1(a,b) a
+#define M_PAIR_2(a,b) b
 
 /* Skip the Nth first arguments
    Generated by:
@@ -2102,29 +2106,45 @@ m_core_hash (const void *str, size_t length)
    Example:
      M_LET(a, STRING_OPLIST) { do something with a }  or
      M_LET(a, b, c, STRING_OPLIST) { do something with a, b & c }
+     M_LET((a, b), c, STRING_OPLIST) { do something with a(init with b) & c }
    NOTE: The user code can not perform a return or a goto within the {}
    other wise the clear code of the object won't be called .
    Last argument can be the oplist or the type itself if a global
    oplist has been recorded for this type.
  */
 #define M_LET(a, ...)                                                   \
-  M_ID(M_LETI1 M_INVERT(a, __VA_ARGS__, M_C3(local_cont_, a, __LINE__) ))
+  M_ID(M_LETI1 M_INVERT(a, __VA_ARGS__,                                 \
+                        M_IF(M_PARENTHESIS_P(a))(M_LETI_VAR_NAME_A,     \
+                                                 M_LETI_VAR_NAME_B)(a) ))
 
+// 1b. Generate a unique name based on the first variable and the line number
+#define M_LETI_VAR_NAME_A(var) M_C3(_local_cont_, M_RET_ARG1 var, __LINE__)
+#define M_LETI_VAR_NAME_B(var) M_C3(_local_cont_, var, __LINE__)
+// 2. Evaluate with or without 
 #define M_LETI1(cont, oplist, ...)                                      \
   M_LETI2(cont, M_GLOBAL_OPLIST(oplist), __VA_ARGS__)
-
+// 3. Map all variables to their own LET
 #define M_LETI2(cont, oplist, ...)                                      \
   for(bool cont = true; cont ; /* unused */)                            \
-    M_MAP2(M_LETI_SINGLE, (cont, oplist,), __VA_ARGS__)
-
-#define M_LETI_SINGLE(data, name)                               \
-  M_LETI_SINGLE2(M_RET_ARG1 data, M_RET_ARG2 data, name)
-
+    M_MAP2(M_LETI_SINGLE, (cont, oplist), __VA_ARGS__)
+// 4. Dispatch the right LET in function of having or not arguments 
+#define M_LETI_SINGLE(data, name)                                       \
+  M_IF(M_PARENTHESIS_P(name))(                                          \
+      M_LETI_SINGLE2_SET(M_PAIR_1 data, M_PAIR_2 data, M_PAIR_1 name, M_PAIR_2 name), \
+      M_LETI_SINGLE2(M_PAIR_1 data, M_PAIR_2 data, name))
+// 5a. Define without argument ==> use INIT
 #define M_LETI_SINGLE2(cont, oplist, name)                              \
   for(M_GET_TYPE oplist name;                                           \
       cont && (M_GET_INIT oplist (name), true);                         \
       (M_GET_CLEAR oplist (name), cont = false))                        \
     for(;cont;cont = false)
+// 5b. Define with arguments ==> use INIT_SET (INIT_WITH support pending)
+#define M_LETI_SINGLE2_SET(cont, oplist, name, val)                     \
+  for(M_GET_TYPE oplist name;                                           \
+      cont && (M_GET_INIT_SET oplist (name, val), true);                \
+      (M_GET_CLEAR oplist (name), cont = false))                        \
+    for(;cont;cont = false)
+
 
 /* Transform the va list by adding their number as the first argument of
    the list.

tests/test-mcore.c

@@ -173,6 +173,9 @@ static void test_let(void)
 {
   M_LET(z, M_CLASSIC_OPLIST(testobj)) {
     testobj_add(z,z,z);
+    M_LET((zz,z), M_CLASSIC_OPLIST(testobj)) {
+      testobj_add(zz,zz,z);
+    }
     break;
     assert(0);
   }