Enumeration

Syntax#

function Enumeration’Image (Argument : Enumeration’Base) return String;
function Enumeration’Img return String; — GNAT
function Enumeration’Val (Argument : Universal_Integer) return Enumeration’Base;
function Enumeration’Pos (Argument : Enumeration’Base) return Universal_Integer;
function Enumeration’Enum_Rep (Argument : Enumeration’Base) return Universal_Integer;
function Literal‘Enum_Rep return Universal_Integer; — GNAT
function Literal‘Address return System.Address;
for Enumeration use (Literal_1 => Universal_Integer, Literal_n => Universal_Integer);
(Literal in Enumeration) return Boolean;

Iterating literals

A literal inside a enumeration is a discrete type so we can use attribute Image to find out which literal it is as text form. Notice that this prints out the same word as in the code (but in upper case).

with Ada.Text_IO; use Ada.Text_IO;

procedure Main is
   type Fruit is (Banana, Pear, Orange, Melon);
begin
   for I in Fruit loop
      Put (Fruit'Image (I));
      New_Line;
   end loop;
end;

Result

BANANA
PEAR
ORANGE
MELON

Using package Enumeration_IO

Instead of attribute Image and Ada.Text_IO.Put on enumeration literals we can only use the generic package Ada.Text_IO.Enumeration_IO to print out the literals.

with Ada.Text_IO; use Ada.Text_IO;

procedure Main is
   type Fruit is (Banana, Pear, Orange, Melon);
   package Fruit_IO is new Enumeration_IO (Fruit); use Fruit_IO;
begin
   for I in Fruit loop
      Put (I);
      New_Line;
   end loop;
end;

Result

BANANA
PEAR
ORANGE
MELON

First character upper case rest lower case literals

Attribute Image capitalizes all characters of enumeration literals. The function Case_Rule_For_Names applies upper case for the first character and makes the rest lower case.

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Strings.Maps.Constants; use Ada.Strings.Maps.Constants;
with Ada.Strings.Fixed; use Ada.Strings.Fixed;

procedure Main is
   type Fruit is (Banana, Pear, Orange, Melon);
   function Case_Rule_For_Names (Item : String) return String is
   begin
      return Translate (Item (Item'First .. Item'First), Upper_Case_Map) & Translate (Item (Item'First + 1 .. Item'Last), Lower_Case_Map);
   end;
begin
   for I in Fruit loop
      Put (Case_Rule_For_Names (Fruit'Image (I)));
      New_Line;
   end loop;
end;

Result

Banana
Pear
Orange
Melon

Title Case, Using Enumeration_IO, For a Subrange

Combining change of character case with Enumeration_IO and using a text buffer for the image. The first character is manipulated in place.

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Characters.Handling; use Ada.Characters.Handling;

procedure Main is
    type Fruit is (Banana, Pear, Orange, Melon);
    package Fruit_IO is new Enumeration_IO (Fruit);
    Buffer : String (1 .. Fruit'Width);
begin
   for I in Fruit range Pear .. Fruit'Last loop
       Fruit_IO.Put (To => Buffer,
                     Item => I,
                     Set => Lower_Case);
       Buffer (Buffer'First) := To_Upper (Buffer (Buffer'First));
       Put_Line (Buffer);
   end loop;
end;

Result

Pear  
Orange
Melon