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6.1.4 Type Declaration

A type declaration looks like this:

       type_identifier = type_definition;
       type_identifier = type_definition;

or, with preset content:

       type_identifier = type_definition value constant_expression;
       type_identifier = type_definition value constant_expression;

A type declaration part begins with the reserved word type. It declares a type_identifier which is defined by type_definition. A type definition either can be an array, a record, a schema, a set, an object, a subrange, an enumerated type, a pointer to another type_identifier or simply another type_identifier which is to alias. If a schema type is to be declared, type_identifier is followed by a discriminant enclosed in parentheses:

     type_identifier (discriminant) = schema_type_definition;

If value is specified, followed by a constant satisfying the type definition, every variable of this type is initialized with constant_expression, unless it is initialized by value itself. The reserved word value can be replaced by =, however value is not allowed in ISO-Pascal and Borland Pascal, and the replacement by = is not allowed in Extended Pascal.

Type declaration example

       { This side is the }     { That side is the }
       { type declaration }     { type definition  }
       Arrayfoo            = array [0 .. 9] of Integer;  { array definition }
       Recordfoo           = record                      { record definition }
                               Bar: Integer;
            { schema def with discriminants ``x, y: Integer'' }
       SchemaFoo (x, y: Integer) = array [x .. y] of Integer;
       CharSetFoo          = set of Char;              { Def of a set }
       ObjectFoo           = object                    { Def of an object }
                               procedure DoAction;
                               constructor Init;
                               destructor Done;
       SubrangeFoo         = -123..456;                { subrange def }
       EnumeratedFoo       = (Pope,John,the,Second);   { enum type def }
            { Def of a pointer to another type identifier }
       PInteger            = ^arrayfoo;
            { Def of an alias name for another type identifier }
       IdentityFoo         = Integer;
            { Def of an integer which was initialized by 123 }
       InitializedFoo      = Integer value 123;

See also

Type Definition, Data Types, Variable Declaration