Constant Declarations

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TMT Pascal Language Description

Pascal Language Structure

Constants

Constant Declarations

There are two types of constants and TMT Pascal interprets them both differently.

Constants that are declared without a type may not be changed in the program. Constants that are typed are the same as variables (described below), however they contain an initial value. These constants may be changed in the program. A constant declaration is preceded bythe const reserved word.

const
  identifier [:IdentifierType] = expression;

Identifier is the actual name of the constant defined. IdentifierType, which is optional, specifies the type of the constant. Again, if a type is specified, the constant is the same as a variable with an initial value.

Expression is assigned to the constant and must be evaluated at compile time. The following are untyped constants and may not be modified:

const
  Digit   = '0'..'9';
  MaxSize = 100;
  Msg     = 'This is a string constant';

Typed constants may be of any type except for file, procedure, or function. Some examples of typed constants are:

type
  Coordinate = record
    x,y: Integer;
  end;
const
  Originpos: Coordinate = (x:0; y:0);
  Name     : String = 'Hello World!';
  StrSize  : Integer = 100;
  Ary      : array [False..True] of Byte = (10,15);

See also:
Integer and Real Number Constants
String Constants


String Constants	Table of Content	Types

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