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.