3.3.3 Set types

Free Pascal supports the set types as in Turbo Pascal. The prototype of a set declaration is:

_________________________________________________________________________________________________________ Set Types
-- --set type-set- of -ordinal type------------------------------------
___________________________________________________________________

Each of the elements of SetType must be of type TargetType. TargetType can be any ordinal type with a range between 0 and 255. A set can contain maximally 255 elements. The following are valid set declaration:

Type
  Junk = Set of Char;

  Days = (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
  WorkDays : Set of days;

Given this set declarations, the following assignment is legal:

WorkDays := [ Mon, Tue, Wed, Thu, Fri];

The operators and functions for manipulations of sets are listed in table (3.6).

Table 3.6:

Set Manipulation operators

Operation	Operator
Union	+
Dierence	-
Intersection	*
Add element	include
Delete element	exclude

Two sets can be compared with the <> and = operators, but not (yet) with the < and > operators. The compiler stores small sets (less than 32 elements) in a Longint, if the type range allows it. This allows for faster processing and decreases program size. Otherwise, sets are stored in 32 bytes.

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include and exclude operators

The include and exclude operators are in fact procedures (like Inc and Dec), i.e. use the statements Include(Set, Element); Exclude(Set, Element); to include/exclude Element to/from Set. Note: You could also do Set += [Element]; Set -= [Element];

-- Bram Kuijvenhoven on March 27, 2006 12:29 PM (view details)