Quick start manual

5-18 Delphi Language Guide
Structured types
Sets
A set is a collection of values of the same ordinal type. The values have no inherent
order, nor is it meaningful for a value to be included twice in a set.
The range of a set type is the power set of a specific ordinal type, called the base type;
that is, the possible values of the set type are all the subsets of the base type,
including the empty set. The base type can have no more than 256 possible values,
and their ordinalities must fall between 0 and 255. Any construction of the form
set of baseType
where baseType is an appropriate ordinal type, identifies a set type.
Because of the size limitations for base types, set types are usually defined with
subranges. For example, the declarations
type
TSomeInts = 1..250;
TIntSet = set of TSomeInts;
create a set type called TIntSet whose values are collections of integers in the range
from 1 to 250. You could accomplish the same thing with
type TIntSet = set of 1..250;
Given this declaration, you can create a sets like this:
var Set1, Set2: TIntSet;
ƒ
Set1 := [1, 3, 5, 7, 9];
Set2 := [2, 4, 6, 8, 10]
You can also use the set of ... construction directly in variable declarations:
var MySet: set of 'a'..'z';
ƒ
MySet := ['a','b','c'];
Other examples of set types include
set of Byte
set of (Club, Diamond, Heart, Spade)
set of Char;
The in operator tests set membership:
if 'a' in MySet then ... { do something } ;
Every set type can hold the empty set, denoted by []. For more information about
sets, see “Set constructors” on page 4-14 and “Set operators” on page 4-11.