x << y -- a binary operator usually used for file output.
<< y -- a unary operator usually used for output to stdout.
This operator may be used as a binary operator in an expression like x << y. The user may install binary methods for handling such expressions with code such as
X << Y := (x,y) -> ...where X is the class of x and Y is the class of y.
This operator may be used as a prefix unary operator in an expression like << y. The user may install a method for handling such expressions with code such as
<< Y := (y) -> ...where Y is the class of y.
Methods for << :