Add some comments.

m-algo.h

@@ -36,16 +36,22 @@
   ALGOI_DEF(name, M_GET_TYPE cont_oplist, cont_oplist,                  \
             M_GET_SUBTYPE cont_oplist, M_GET_OPLIST cont_oplist, M_GET_IT_TYPE cont_oplist)
 
+/* MAP a function into all elements of a container.
+   USAGE: ALGO_MAP(container, containerOplist, func[, extra arguments of function]) */
 #define ALGO_MAP(container, cont_oplist, ...)                  \
   M_IF_NARGS_EQ1(__VA_ARGS__)                                  \
   (ALGOI_MAP(container, cont_oplist, __VA_ARGS__),             \
    ALGOI_MAP_ARG(container, cont_oplist, __VA_ARGS__ ))
 
+/* Extract a subset of a container into another.
+   USAGE: ALGO_EXTRACT(containerDest, containerDestOplist, containerSrc, containerSrcOplist, func[, extra arguments of function]) */
 #define ALGO_EXTRACT(contD, contDop, contS, contSop, ...)                \
   M_IF_NARGS_EQ1(__VA_ARGS__)                                           \
   (ALGOI_EXTRACT(contD, contDop, contS, contSop, __VA_ARGS__),          \
    ALGOI_EXTRACT_ARG(contD, contDop, contS, contSop, __VA_ARGS__ ))
 
+/* Perform a Reduce operation over a container.
+   USAGE: ALGO_REDUCE(destVar, container, containerOplist, reduceFunc[, mapFunc[, extraParameters of map function]]) */
 #define ALGO_REDUCE(dest, cont, contOp,  ...)                           \
   M_IF_NARGS_EQ1(__VA_ARGS__)                                           \
   (ALGOI_REDUCE(dest, cont, contOp, __VA_ARGS__),                       \
@@ -53,6 +59,8 @@
     (ALGOI_REDUCE_MAP(dest, cont, contOp, __VA_ARGS__),                 \
      ALGOI_REDUCE_MAP_ARG(dest, cont, contOp, __VA_ARGS__) ) )
 
+/* Initialize a container by a variable array list.
+   USAGE: ALGO_INIT_VA(container, containerOplist, param1, param2, param3) */
 #define ALGO_INIT_VA(dest, contOp, ...) do {            \
     M_GET_INIT contOp (dest);                           \
     M_MAP2(ALGOI_INIT_VA_FUNC, (dest, M_GET_PUSH contOp, ) , __VA_ARGS__); \