◄Syntax►  ◄Details►  ◄Example►                 ◄Contents►  ◄Index►  ◄Back►
──────────────────────────────────────────────────────────────────────────────
CONST declares symbolic constants for use in place of values.
 
CONST constantname = expression [,constantname = expression]...
    ■ The expression can consist of literals (such as 1.0), other
      constants, or any of the arithmetic and logical operators except
      exponentiation (^). You also can use a single literal string such
      as "Error on input." You cannot use string concatenation,
      variables, user-defined functions, or intrinsic functions--such as
      SIN or CHR$--in expressions assigned to constants.
 
Usage Notes
    ■ If you use a type-declaration character in the name, you can omit the
      character when the name is used, as shown in the following example:
 
        CONST MAXDIM% = 250
        .
        .
        .
        DIM AccountNames$(MAXDIM)
 
    ■ If you omit the type-declaration character, the constant is given a
      type based on the expression in the CONST statement. Strings always
      yield a string constant. With numeric expressions, the expression is
      evaluated and the constant is given the simplest type that can
      represent the constant. For example, if the expression gives a result
      that can be represented as an integer, the constant is given an
      integer type.
    ■ Names of constants are not affected by DEFtype statements such as
      DEFINT. A constant's type is determined either by an explicit
      type-declaration character or by the type of the expression.
    ■ Constants must be defined before they are referred to. The following
      example produces an error because the constant ONE is not defined
      before it is used to define TWO (constants are defined from
      left to right):
 
        CONST TWO = ONE + ONE, ONE = 1
 
    ■ Constants declared in a SUB or FUNCTION procedure are local to the
      SUB or FUNCTION. A constant declared outside a procedure is defined
      throughout the module. You can use constants anywhere that you would
      use an expression.
    ■ A common programming practice is to use a statement such as the
      following (any non-zero value represents "true"):
 
        TRUE=-1
 
    ■ Using constants offers several advantages over using variables for
      constant values:
        - You need only define constants once for an entire module.
        - Constants cannot be inadvertently changed.
        - In stand-alone programs, using constants produces faster and
          often smaller code than using variables.
        - Constants make programs easier to modify.