嵌套的 case 语句（nested case statements）

可以将case statement作为外部case statement的语句序列的一部分。 即使内部和外部的case constants包含共同的值，也不会产生冲突。

语法 (Syntax)

嵌套case语句的语法如下 -

case (ch1) of
   'A': begin
      writeln('This A is part of outer case' );
         case(ch2) of
            'A': writeln('This A is part of inner case' );
            'B': (* case code *)
            ...
         end; {end of inner case}
      end; (* end of case 'A' of outer statement *)
   'B': (* case code *)
   'C': (* case code *)
   ...
end; {end of outer case}

例子 (Example)

以下程序说明了这个概念。

program checknestedCase;
var
   a, b: integer;
begin
   a := 100;
   b := 200;
   case (a) of
      100: begin
         writeln('This  is part of outer statement' );
         case (b) of
            200: writeln('This  is part of inner statement' );
            end;
         end; 
      end;
   writeln('Exact value of a is : ', a );
   writeln('Exact value of b is : ', b );
end.

编译并执行上述代码时，会产生以下结果 -

This is part of outer switch
This is part of inner switch
Exact value of a is: 100
Exact value of b is: 200