Description of the illustration character_expression.eps

 { character_constant
   | character_function_call
   | character_literal
   | character_variable
   | placeholder]
 }
 [|| { character_constant
       | character_function_call
       | character_literal
       | character_variable
       | placeholder]
      } 
 [|| { character_constant
       | character_function_call
       | character_literal
       | character_variable
       | placeholder]
     } ]...