What are sets in Pascal?

Defining sets

The following example shows the set being defined followed by variables of that set type being declared:

type
set-name = set of base type;

var
Months = (January, February, March, April, May, June, July, August, September, October, November, December);

Letters = set of char;

Alphabets = set of 'A' .. 'Z';

Set operations

The following operations can be performed on sets:

Operation	Description
Union	Gives a new set containing all the members of the sets on which union has been performed
Intersection	Gives a new set containing only the common members of the sets on which intersection has been performed
Difference	Gives a new set containing members that are not common to either set on which difference has been performed
Symmetric Difference	Gives a new set containing those members of the sets not in the intersection but in either of the sets on which symmetric difference has been performed
Inclusion	If all the elements of Set 1 are in Set 2 but not vice versa
In	Checks if a certain element is present in a set or not

Set operators

The following table shows different set operators and their descriptions given the following:

S1 := [‘1’, ‘2’, ‘3’, ‘4’];

S2 := [‘3’, ‘4’, ‘5’, ‘6’, ‘7’];

Operator	Description	Example
`+`	Union	S1 `+` S2 = [‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘6’, ‘7’]
`*`	Intersection	S1 `*` S2 = [‘3’, ‘4’]
`-`	Difference	S1 `-` S2 = [‘1’, '2,]
`><`	Symmetric Difference	S1 `><` S2 = [‘1’, ‘2’, ‘5’, ‘6’, ‘7’]
`=`	Equality	S1 `=` S2 gives the boolean value False
`<>`	Non-equality	S1 `=` S2 gives the boolean value True
`<=`	Contains (if one set is a subset of the other)	S1 `=` S2 gives the boolean value False
`Include`	Includes an element in the set	`Include` (S1, [‘5’]) will give a set [‘1’, ‘2’, ‘3’, ‘4’, ‘5’]
`Exclude`	Excludes an element from the set	`Exclude` (S1, [‘4’]) will give a set [‘1’, ‘2’, ‘3’]
`In`	If a certain element is a member of a set or not	[‘1’] in S1 gives the boolean value True

program setFurniture;
type  
furniture = (bed, side_table, dressing_table, dining_table, chair, cupboard);  
furnitures = set of furniture;  
 
procedure displayFurnitures(f : furnitures);  
const  
list : array [furniture] of String[14]  
  = ('bed', 'side_table', 'dressing_table', 'dining_table', 'chair', 'cupboard');  
var  
   fr : furniture;  
   s : String;  
begin  
   s:= ' ';  
   for fr := bed to cupboard do  
      if fr in f then  
      begin  
         if (s<>' ') then s := s +' , ';  
         s := s + list[fr];  
      end;   
      
    writeln('[',s,']');  
end;  
 
var  
   drawing_room, bed_room, f : furnitures;  
   isTrue : boolean;
 
begin  
   f := [bed, side_table, dressing_table, dining_table, chair, cupboard];
   displayFurnitures(f);
   
   drawing_room := [side_table, chair, dining_table];
   bed_room := [bed, side_table, dressing_table, cupboard];
   f := drawing_room + bed_room; {union}
   displayFurnitures(f);
   drawing_room := [side_table, chair, dining_table];
   bed_room := [bed, side_table, dressing_table, cupboard];
   f := drawing_room * bed_room; {intersection}
   displayFurnitures(f);
   
   drawing_room := [side_table, chair, dining_table];
   bed_room := [bed, side_table, dressing_table, cupboard];
   f := drawing_room - bed_room; {difference}
   displayFurnitures(f);
   
   
   drawing_room := [side_table, chair, dining_table];
   bed_room := [bed, side_table, dressing_table, cupboard];
   f := drawing_room - bed_room; {symmetric difference}
   displayFurnitures(f);
   
   
   isTrue := [bed, side_table, dressing_table, dining_table] = [dining_table, chair, cupboard]; {equality}
   writeln(isTrue);
   
   isTrue := [bed, side_table, dressing_table, dining_table] <= [dining_table, chair, cupboard]; {nonequality}
   writeln(isTrue);
   
  
end.

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What are sets in Pascal?

Defining sets

Set operations

Set operators

Example