IDENTIFIER: /[A-Za-z_?!][A-Za-z0-9_?!]*/
INTEGER: ("0".."9")+
COMMENT: "//" /[^\n]*/

top_level_compound: top_level_single* -> multi

top_level_single: "function" IDENTIFIER arg_list multi_stmt? "end" -> function
                | "procedure" IDENTIFIER multi_stmt? "end" -> procedure
                | "structure" IDENTIFIER *IDENTIFIER "end"
                | "const" IDENTIFIER "=" expr

multi_stmt: stmt (";"? stmt)* -> multi

stmt: expr -> const
    | "return" expr -> return_
    | "break" -> break_
    | "if" expr "then" multi_stmt? ("elseif" expr "then" multi_stmt?)* "end" -> if_no_else
    | "if" expr "then" multi_stmt? ("elseif" expr "then" multi_stmt?)* "else" multi_stmt? "end" -> if_else
    | "while" expr "do" multi_stmt? "end" -> while_
    | IDENTIFIER "=" expr -> assign

expr: sum -> const
    | expr "." expr -> get_attr
    | bool_sum -> const
    | list -> const
    | range_literal -> const
    | expr arg_list -> func_call
    | expr "==" expr -> eq
    | expr ">" expr -> gt
    | expr "<" expr -> lt
    | expr ">=" expr -> ge
    | expr "<=" expr -> le
    | "#" expr -> length

list: "[" compound_expr "]" -> list_
    | "[]" -> list_

arg_list: "(" compound_expr ")" -> list_
    | "()" -> list

range_literal: "{" atom ".." atom "}" -> range

compound_expr: expr ("," expr)* -> multi

bool_sum: bool_product -> const
        | bool_sum "or" bool_product -> or_

bool_product: bool -> const
            | bool_product "and" bool -> and_

bool: "true" -> boolt
    | "false" -> boolf
    | "not" bool -> not_
    | "(" bool_sum ")" -> const

sum: product -> const
   | sum "+" product -> add
   | sum "-" product -> sub

product: atom -> const
       | product "*" atom -> mul
       | product "/" atom -> div
       | product "%" atom -> mod

atom: INTEGER -> num
    | IDENTIFIER -> iden
    | ESCAPED_STRING -> string
    | "(" sum ")" -> const

%import common.WS
%import common.ESCAPED_STRING

%ignore WS
%ignore COMMENT