Statements in Ada

simple_statement ::= null_statement
   | assignment_statement     | exit_statement
   | procedure_call_statement | raise_statement
   | return_statement        

compound_statement ::=
     if_statement
   | case_statement
   | loop_statement
   | block_statement

null_statement ::= null;

statement_identifier ::= direct_name

Assignment

assignment_statement ::=
   variable_name := expression;

Examples

Value  := Max_Value - 1;
Shade  := Blue;
U      := Dot_Product (V, W);
Writer := (Status => Open, Unit => Printer, Line_Count => 60);

Conditional

if_statement ::=
    if condition then
      sequence_of_statements
   {elsif condition then
      sequence_of_statements}
   [else
      sequence_of_statements]
    end if;

condition ::= boolean_expression

case_statement ::=
   case expression is
       case_statement_alternative
      {case_statement_alternative}
   end case;

case_statement_alternative ::=
   when discrete_choice_list =>
      sequence_of_statements

Example programs:

• days.adb
• grade.adb
• telephone.adb
• parse.adb
• craps.adb

Loop

loop_statement ::=
   [loop_statement_identifier:]
      [iteration_scheme] loop
         sequence_of_statements
       end loop [loop_statement_identifier];

iteration_scheme ::= while condition
   | for loop_parameter_specification

loop_parameter_specification ::=
   defining_identifier in [reverse] discrete_subtype_definition

Example programs:

• while
• for

Block

block_statement ::=
   [block_identifier:]
       [declare
            declarative_part]
        begin
            handled_sequence_of_statements
        end [block_identifier];

Example

Swap: declare
   Temp : Integer;
begin
   Temp := V; V := U; U := Temp;
end Swap;