is the function composition operator.

  is the repeated function composition operator.

If n is negative, the  table is checked to see if it has an entry for f.  That is, if , then .

Composition also applies to procedures.  However, given two procedures f and g, the composition  is of type function, not type procedure.  For more information, see type/function and type/procedure.

(sin@cos)(x);

(sin@arcsin)(x);

sin@arcsin;

simplify((3));

sin@@0;

sin@@1;

(sin@@2)(x);

cos@@(-1);

(D@@2)(ln);

The @ and @@ operators are thread-safe as of Maple 15.

For more information on thread safety, see index/threadsafe.