ADA Data Structures

1
ADAData Structures

• Subtype
• Enumeration type

2
SUBTYPE

• Definition
• A subset of the values associated
• with the original type.
• Example
• SUBTYPE Natural IS Integer RANGE 0..IntegerLast
• SUBTYPE Positive IS Integer RANGE 0..IntegerLast

3
More Examples

• SUBTYPE SmallInt IS Integer RANGE -50. .50
• SUBTYPE NonNegFloat IS Float RANGE 0.0 . .
  FloatLast
• SUBTYPE CapLetter IS Character RANGE A.
  .Z
• X, Y, Z SmallInt
• NextChar CapLetter
• Hours_Worked NonNegFloat

4
Constraint Error

• SUBTYPE SmallInt IS Integer RANGE -50. .50
• 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
• V1V2 leads to compilation error

6
More Compatibility

• Example
• SUBTYPE SmallInt IS Integer RANGE -50. .50
  
• V1 Integer
• V2 SmallInt
• V1 V2 is Compatible.

7
More Compatibility

• Two values are compatible if they have
• the same type name
• or
• one values type is a subtype of the other
  values 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

• Typeattribute-name
• Typeattribute-name(value)
• Example
• DaysFirst
• DaysSucc(Friday)
• DaysPos(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 gt type)

19
Get Examples

• PACKAGE Day_IO IS NEW Ada.Text_IO.Enumeration (
  Enum gt Dats )
• Day_IO.Get ( Item gt Some_day)
• Day_IO.Get ( Item gt Valentine_Day)

20
Put Examples

• Day_IO.Put
• ( Item gt Some_Day, width gt 5, Set gt
  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 gt
  English_Colors)
• Package Fr_Color_IO is
• New Ada.Text_IO.Enumeration_IO (Enum gt
  French_Colors)

22

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