Chapter 6. Statements
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Chapter 6. Statements

Table of Contents

6.1. Block Statements
6.2. If Statements
6.3. Iteration Statements
6.4. Assignment Statements

This chapter defines the statements of the Comma programming language.

Statement
[52]Statement::= Block_Statement | Null_Statement | Iteration_Statement | Assignment_Statement  
[53]Null_Statement::=null 

A null statement consists of the single reserved word null and has no effect.

6.1. Block Statements

Block Statement
[54]Block_Statement::= [ Identifier : ] [ declare { Declarative Item } ]
begin Sequence_Of_Statements end [ Identifier ] 		 
[55]Sequence_Of_Statements::= Statement ; { Statement ; }  

6.2. If Statements

If Statement
[56]If_Statement::= if Expression then Sequence_Of_Statements
{ elsif Expression then Sequence_Of_Statements }
[ else Sequence_Of_Statements ]
end if 		 

Example 6.1. Examples of if statements:

      function Fib (X : Natural) return Natural is
      begin
         if X = 0 then
            return 0;
         elsif X = 1 then
            return 1;
         else
            return Fib(X - 2) + Fib(X - 1);
         end if;
      end Fib;

6.3. Iteration Statements

Iteration Statement
[57]Iteration_Statement::= [ Loop_Tag : ] Loop_Body [ Loop_Tag ]  
[58]Loop_Tag::= Identifier  
[59]Loop_Body::= Loop_Statement | While_Statement | For_Statement  
[60]Loop_Statement::= loop Sequence_Of_Statements end loop  
[61]While_Statement::= while Expression loop Sequence_Of_Statements end loop  
[62]For_Statement::= for Identifier in Discrete_Subtype_Definition loop Sequence_Of_Statements end loop  

Example 6.2. Examples of iteration statements:

      type Data is array (Positive range <>) of Integer;

      procedure Sort (V : in out Data) is
      begin
         if V'Length < 2 then
            return;
         end if;

         loop
            declare
               J      : Integer;
               Tmp    : Integer;
               Sorted : Boolean := true;
            begin
               for I in V'First .. V'Last - 1 loop
                  J := I + 1;
                  if V(J) < V(I) then
                     Tmp    := V(I);
                     V(I)   := V(J);
                     V(J)   := Tmp;
                     Sorted := false;
                  end if;
               end loop;

               exit when Sorted;
            end;
         end loop;
      end Sort;

6.4. Assignment Statements

Assignment Statement
[63]Assignment_Statement::= Name := Expression  
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