Literals

• Underscores allowed:
  • Example: 111_222_333, 1011_0000, 1_000.0

• Bases 2-16:
  • Example 1: 2#0011_1100_0000#, 16#F1F1_ABCD#

• For floats, digits required on both sides of decimal point
  • Example: 0.0 is okay, but 0. and .0 are not

• Exponents are allowed:
  • Example 1: 214E3 = 214_000
  • Example 2: 1.0E3 = 1_000.0, 1.0E-1 = 0.1
  • Example 3: 2#110#E3 is (1*2**2 + 1*2**1 + 0*2**0) * 2**3

• Character Example: 'A'

• String Examples: "Hello", ""

Enumeration Literals

• Normally enumeration literals are identifiers
• Enumeration literals can also be Characters
• Example:

          type Character is ('a', 'b', ...);
  
          type Weird is (Red, Blue, 'G');
  
          type Weirder is ('a', 'A', A);
  
          w: Weird := Red;
          x: Weirder := 'a';
          ...
          w := 'G';
          x := A;
       

• The only difference between character and identifier enumeration literals involves some visibility issues which we are not ready to discuss yet.

Identifiers

• Identifiers (ie variables, types, enumerated values) begin with a letter which can be followed by any number of letters or digits or underscores. Underscores can only appear between two non-underscores.

• Reserved words cannot be used as identifiers.

• Predefined types and values can be used as identifiers.

• Example: dontEverDoThis.adb