compliment = "--" primary / primary;

   (symbol for up arrow) means mod. and /\ means exclusive or.

   Notice that the uniary minus is allowable, and parsed so you can
   write x*-y.

   Since there is no standard convention with bitwise operators, they
   all have the same precedence, and parentheses must be used for
   grouping.

   Compliment is the l's compliment.

   It is assumed that all arithmetic and bit operations take place in
   the mode and style of the machine running the code.  Anyone who
   takes advantage of word lengths, two's compliment arithmetic, etc.
   will eventually have problems.

PRIMARY

   SYNTAX

      primary =

         constant /

         builtin /

         variable / (

         block /

         '( exp ');

      variable = .id (

         '(symbol for left arrow) exp /

         '( block ') /

         .empty);

      constant =  integer / real / string;

      builtin =

         mesinfo /

         cortnin /

         ("MIN" / "MAX") exp $('. exp) '/ ;

   parenthesized expressions may be a series of expressions.  The
   value of a series is the value of the last one executed at run time.

   Subroutines may have one call by name argument.

   Expressions may be mixed.  Strings are a big problem?  Rulifson
   also wants to get rid of real numbers!!

CONJUNCTIVE EXPRESSION

   SYNTAX

      conjunct = disjunct ("AND" conjunct / .empty);

      disjunct = negation ("OR" negation / .empty);

      negation = "NOT" relation / relation;

      relation =

         '( conjunct ') /

         sum (

           "<=" sum /

           ">=" sum /

           '< sum /

           '> sum /

           '= sum /

           '" sum /

           .empty);

   The conjunct construct is rigged in such a way that a conjunct
   which is not a sum need not have a value, and may be evaluated
   using jumps in the code.  Reference to the conjunct is made only
   in places where a logical decision is called for (e.g. if and
   while statements).

   We hope that most compilers will be smart enough to skip
   unnecessary evaluations at run time.  I.e a conjunct in which the
   left part is false or a disjunct with the left part true need not