Allowing ArithmeticExpression to be a Statement

For function returning an arithmetic or a boolean expression like

equal?(x: %, y: %): Boolean == (x.n) = (y.n); 

it may be useful to add the rule

Statement

$\longmapsto$

RightValue

where RightValue is now defined by

RightValue	$\longmapsto$	FunctionCall
RightValue	$\longmapsto$	ArithmeticExpression
RightValue	$\longmapsto$	BooleanExpression

You may also refuse the above function definition and prefer

equal?(x: %, y: %): Boolean == return ((x.n) = (y.n)); 

as in JAVA.