digit : '0' | '1' |'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9';
digits : digit + ;
number : (digits 'r')? '-' ? digits ( '.' digits )? ('e' '-' ? digits)? ;
letter : 'A' "[...]" 'Z' | 'a' "[...]" 'z' ;
special_character : '+' | '/' | '\' | '*' |'~'|'<'|'>'|'='|'@'|'%'| '|' |'&'|'?' | '!'|',';
character : ('[' | ']' | '{' | '}' | '(' | ')' | '^' | ';' | '$' | '#' | ':' | '.' | "'" )
          | (digit | letter | special_character) ;
return_operator : '^'; 
assignment_operator : ":=" ;
identifier : letter ( letter | digit ) * ;
symbol : identifier | binary_selector | keyword + ;
symbol_constant : '#' symbol ;
character_constant : '$' (character | "'" | '"') ;
string : "'" ( character | (("'" "'") | '"' ) ) * "'" ;
comment : '"' ( character | (('"' '"') | "'") ) * '"' ;
array :  '('  ( number | symbol |string | character_constant | array ) * ')' ;
array_constant : '#' array ;
literal : number | symbol_constant | character_constant | string | array_constant ;
variable_name : identifier;
unary_selector : identifier;
binary_selector : ('-' | special_character) special_character ? ;
keyword : identifier ':' ; 
primary : variable_name | literal | block | ( '(' expression ')' ) ;
unary_object_description : primary | binary_expression ;
binary_object_description : unary_object_description | binary_expression;
unary_expression : unary_object_description  binary_expression ;
binary_expression : binary_object_description binary_selector  unary_object_description ;
keyword_expression : unary_object_description ( keyword binary_object_description)+ ;
message_expression : unary_expression | binary_expression | keyword_expression ;
cascaded_message_expression : message_expression (
  ';' ( unary_selector  
  | (binary_selector  unary_object_description) 
  | (keyword binary_object_description )+
))* ;
expression : ( (variable_name assignment_operator)+ )? 
(primary | message_expression | cascaded_message_expression); 
statements : (return_operator expression '.' ? ) |
 (expression ('.' statements *)?);
 block : '[' 
          (
            ((':' variable_name)+ '|' statements) ?
          | 
          statements
          )
          ']' ;
temporaries : '|' variable_name * '|' ;
message_pattern :  unary_selector | binary_selector | (keyword variable_name)+; 
method : message_pattern ( (temporaries statements) |statements ? );