Arithmetic operators

  There are two assignment operators for use with arithmetic
  expressions:
              =  equals
              <- jam transfer

  Where the = operator is used, the expression on the right-hand side is
  evaluated and the value obtained is assigned to the destination
  indicated by the left-hand side, provided that the lengths and types
  are compatible.  A fault occurs if an attempt is made to assign too
  large a value to a variable using this operator.

  Where the <- is used, only as many bits as will fit the location
  designated by the left hand side are assigned, starting with the least
  significant bits.

  In general the arithmetic assignment instruction assigns the result of
  evaluating an arithmetic expression to a variable.  Only the result of
  an integer expression may be assigned to an integer variable, but the
  result of an integer or real expression may be assigned to a real
  variable.
  The following operators may be applied to real and integer variables
  in arithmetic expressions:


        _______________________________________
       |                                       |
       |      +        addition                |
       |      -        subtraction             |
       |      *        multiplication          |
       |      /        real division           |
       |     //        integer division        |
       |      \        real exponentiation     |
       |               (e.g. Y\3 = Y cubed)    |
       |     \\        integer exponentiation  |
       |_______________________________________|

  The established order of precedence for the arithmetic operators is
  given in the following table, starting with the highest.  Operators on
  the same horizontal line of the table have equal precedence.

           _________________________
          |                         |
          |   \       \\            |
          |   *        /       //   |
          |   *        -            |
          |_________________________|


  Parentheses may be used to override the natural order of evaluation of
  an expression or to remove ambiguity.  Where operators are of equal
  precedence, left-hand precedence pertains as in normal mathematical
  usage.
  Examples:
           A-B+C    is equivalent to  (A-B)+C
           A-(B+C)                    (A)-(B+C)
           A/B*C                      (A/B)*C
           A/(B*C)                    (A)/(B*C)
           A**B*C                     (A**B)*C
           A**(B*C)                   (A)**(B*C)

  The one exception to the left-hand precedence rule is that consecutive
  exponentiations are evaluated from right to left; thus A**B**C is
  evaluated as A**(B**C), not as (A**B)**C.