VMS Help PASCAL, Expressions, Operators  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Pascal provides several classes  of  operators.   You  can  form
  complex  expressions  by  using  operators to combine constants,
  constant identifiers, variables, and function designators.

1 - Arithmetic Operators

  An  arithmetic  operator  usually   provides   a   formula   for
  calculating  a value.  To perform arithmetic operations, numeric
  operands are  combined  with  one  or  more  of  the  arithmetic
  operators.

  Arithmetic Operators:

     operator  |  example  |  result
     --------------------------------------------
        +          A + B      Sum of A and B
        -          A - B      B subtracted from A
        *          A * B      Product of A and B
        **         A ** B     A raised to the power of B
        /          A / B      A divided by B
        DIV        A DIV B    Result of A divided by B,
                              truncated toward zero
        REM        A REM B    Remainder of A divided by B
        MOD        A MOD B    Modulus of A with respect to B

2 - Relational Operators

  A  relational  operator  tests  the  relationship  between   two
  ordinal,  real,  DOUBLE,  or QUADRUPLE expressions and returns a
  Boolean value.  If the relationship holds, the result  is  TRUE;
  otherwise  the  result is FALSE.  You can also apply some of the
  relational operators to string operands and to set operators.

  Relational Operators:

     operator  |  example  |  result
     --------------------------------------------
        <>         A <> B     TRUE if A is not equal to B
        <          A < B      TRUE if A is less than B
        <=         A <= B     TRUE if A is less than or equal to B
        >          A > B      TRUE if A is greater than B
        >=         A >= B     TRUE if A is greater than or equal to B

3 - Logical Operators

  A logical operator evaluates one or more Boolean expressions and
  returns a Boolean value.

  Logical Operators:

     operator    |  example       |    result
     -------------------------------------------------
       AND           A AND B         TRUE if both A and B are TRUE

       OR            A OR B          TRUE if either A or B is TRUE,
                                     or if both are TRUE

       NOT           NOT A           TRUE if A is FALSE, and
                                     FALSE if A is TRUE

       AND_THEN      A AND_THEN B    TRUE if both A and B are TRUE
                                     (forces left-to-right evaluation
                                      order with short-circuiting)

       OR_ELSE       A OR_ELSE B     TRUE if either A or B is TRUE,
                                     or if both are TRUE
                                     (forces left-to-right evaluation
                                      order with short-circuiting)

4 - String Operators

  A string  operator  concatenates  or  compares  character-string
  expressions.  The result is either a string or a Boolean value.

  String Operators:

    operator | example |    result
    --------------------------------------------
       +       A +  B   String that is the concatenation of strings

       <>      A <> B   TRUE if strings A and B have unequal ASCII
                        values

       <       A <  B   TRUE if the ASCII value of string A is less
                        than that of string B

       <=      A <= B   TRUE if the ASCII value of string A is less
                        than or equal to that of string B

       >       A >  B   TRUE if the ASCII value of string A is greater
                        than that of string B

       >=      A >= B   TRUE if the ASCII value of string A is greater
                        than or equal to that of string B

5 - Set Operators

  A set operator forms the  union,  intersection,  difference,  or
  exclusive-OR of two sets, compares two sets, or tests an ordinal
  value for inclusion in a set.  Its result is either a set  or  a
  Boolean value.

  Set Operators:

       operator  |  example  |    result
       --------------------------------------------
          +          A + B     Set that is the union of sets A and B
          *          A * B     Set that is the intersection of sets A
                               and B
          -          A - B     Set of those elements in set A that are
                               not also in set B
          <>         A <> B    TRUE if set A is not equal to set B
          <=         A <= B    TRUE if set A is a subset of set B
          >=         A >= B    TRUE if set B is a subset of set A
          IN         C IN B    TRUE if C is an element of set B

6 - Type Cast Operator

  The type cast operator changes the context in which  a  variable
  or an expression of a certain data type can be used.  The actual
  representation of the object being cast is not  altered  by  the
  type  cast  operator.  Compaq Pascal overrides the type only for
  the duration of one operation.  It  has  one  of  the  following
  forms:

     variable-identifier :: type-identifier

     (expression) :: type-identifier

  The type cast operator (::) separates the name of  the  variable
  or  an  expression in parentheses from its target type, the type
  to which it is being cast.

  Example:
     TYPE
        F_Float = PACKED RECORD
                  Frac1 : 0..127;
                  Expo  : 0..255;
                  Sign  : Boolean;
                  Frac2 : 0..65535;
                  END;

     VAR
        A : REAL;

     {In the executable section:}
     A :: F_Float.Expo := A :: F_Float.Expo + 1;

  The  record  type  'F_Float'  illustrates  the  layout   of   an
  F_floating  real  number.   The  real  variable 'A' is cast as a
  record of this type, allowing access to  the  fields  containing
  the  mantissa, exponent, sign, and fraction of 'A'.  Adding 1 to
  the field containing the exponent would give the same result  as
  multiplying 'A' by 2.0.