
?Expr1 =:= ?Expr2

   The value of Expr1 is equal to the value of Expr2.

Arguments
   Expr1               An arithmetic expression
   Expr2               An arithmetic expression

Type
   library(suspend)

Description
   Suspends until both Expr1 and Expr2 are ground, and then both arguments
   are evaluated and compared, succeeding if they are equal (beware of 
   rounding errors when comparing reals).


Resatisfiable
      No

Fail Conditions
      fails if the value of Expr1 is not equal to the value of Expr2



Exceptions
     5 --- Expr1 or Expr2 is not an arithmetic expression.


