1. Subtype Enumeration type
ADA Data Structures
Subtype
Enumeration type

2. SUBTYPE Definition : A subset of the values associated
with the original type.
Example :
SUBTYPE Natural IS Integer RANGE 0..Integer’Last;
SUBTYPE Positive IS Integer RANGE 0..Integer’Last;

3. More Examples SUBTYPE SmallInt IS Integer RANGE -50. .50;
SUBTYPE NonNegFloat IS Float RANGE Float’Last;
SUBTYPE CapLetter IS Character RANGE ‘A’. .’Z’;
X, Y, Z : SmallInt;
NextChar : CapLetter;
Hours_Worked : NonNegFloat;

4. Constraint Error X := 26; Y := 28; Z := X + Y; Compilation Error ?
SUBTYPE SmallInt IS Integer RANGE ;
X, Y, Z : SmallInt;
X := 26;
Y := 28;
Z := X + Y;
Compilation Error ?
At Run Time, Error will be raised. Why ?

5. Compatibility Rules for Types and Subtypes
Do not allow to mix the types of operands
Examples:
v1 : Integer;
V2 : Float;
V1+V2 leads to compilation error

6. More Compatibility Example : V1 : Integer; V2 : SmallInt;
SUBTYPE SmallInt IS Integer RANGE ;
V1 : Integer;
V2 : SmallInt;
V1 + V2 is Compatible.

7. More Compatibility Two values are compatible if they have
the same type name or
one value’s type is a subtype of the other value’s type.

8. Interesting Things X : Integer; Y : Natural; Think about X := Y; and
Y := X;

9. No Compilation Error X := Y; is always valid. But
Y := X; is not always valid at execution time.
When ?

10. Ada Standard Library With Ada.Numerics; Example get the value of Pi as
Ada.Numerics.Pi
do not need to declare Pi as constant float ...

11. Enumeration Type
Defined by a list of values taking the form of identifiers.
Useful in representing a fixed set of values that are not numerical such as days of the week, class year (freshman, sophomore, junior, senior) , etc...

12. Defining Enumeration Type
Form
TYPE enumeration-type ( identifier-list)

13. Examples
TYPE Days IS
(Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday);
Declaration
Some_Day : Days;
Today : Days;
Valentine_Day : Days;

14. More Examples Assignment Statements Today := Friday;
Some_Day := Monday;

15. Type Attributes and Operations
Six important Attributes
First
Last
Pos position for a given value
Val value for a given position
Pred predecessor of a given value
Succ successor of a given value

16. Attribute Query Type’attribute-name Type’attribute-name(value) Example
Days’First
Days’Succ(Friday)
Days’Pos(Sunday)

17. Input/Output for Enumeration Types
Within Ada.Text_IO,
a generic package called “Enumeration_IO” must be used.
But it can not be used immediately.
Instances must be created

18. Format PACKAGE instance IS
NEW Ada.Text_IO.Enumeration_IO (Enum => type);

19. Get Examples
PACKAGE Day_IO IS NEW Ada.Text_IO.Enumeration ( Enum => Dats );
Day_IO.Get ( Item => Some_day);
Day_IO.Get ( Item => Valentine_Day);

20. Put Examples Day_IO.Put
( Item => Some_Day, width => 5, Set => Lower_case);

21. Example Program with Enumeration Type
with Ada.Text_IO;
Procedure Colors Is
Type English_Colors Is
(white, black, red);
Type French_Colors is
(blanc, noir, rouge);
Package Eng_Color_IO is
New Ada.Text_IO.Enumeration_IO (Enum => English_Colors);
Package Fr_Color_IO is
New Ada.Text_IO.Enumeration_IO (Enum => French_Colors);

22. Eng_Color : English_Colors; Fr_Color : French_Colors; position : Natural; Begin -- Ada.Text_IO.Put (Item =>" The first English color is "); Eng_Color_IO.Put(Item => English_Colors'First); Ada.Text_IO.New_Line; Ada.Text_IO.Put (Item => " Enter an English color : "); Eng_Color_IO.Get(Item => Eng_Color); position := English_Colors'Pos(Eng_Color); Fr_Color := French_Colors'Val(position); Ada.Text_IO.Put (Item => " The equavilent French Color is "); Fr_Color_IO.Put (Item => Fr_Color, Set =>Ada.Text_IO.Lower_Case); end Colors;