Relational Expressions

< relational expression >	->	< arithmetic expr. >
	|	< arithmetic expr. > < relational > < arithmetic expr. >
<relational> -> < |> |= |<= |>= |!=

Relational expressions can be used to compare the values produced by two expressions. Note that the syntax of the language prohibits the expression

 a < b < c

 (a < b) < c