BLOCK = { STATEMENT };

STATEMENT = VARIABLE_ASSIGNMENT | PRINT | IF_STATEMENT | WHILE_STATEMENT | FUNCTION_DEFINITION | RETURN_STATEMENT ;

VARIABLE_ASSIGNMENT = IDENTIFIER, "=" EXPRESSION, ";" ;
PRINT = "imprime" "(" EXPRESSION, ")" ";" ;
IF_STATEMENT = "se" "(" CONDITION, ")" BLOCO, ["senao" BLOCO] ;
WHILE_STATEMENT = "enquanto" "(" CONDITION, ")" BLOCO ;
FUNCTION_DEFINITION = "df" IDENTIFIER, "(" PARAMETROS, ")", BLOCO ;
RETURN_STATEMENT = "retorna" [EXPRESSION], ";" ;
BLOCO = "{" {STATEMENT} [RETURN_STATEMENT] "}" ;

PARAMETROS = [IDENTIFIER, {"," IDENTIFIER}] ;

CONDITION = CONDITION_SIMPLE, { LOGICAL_OPERATOR CONDITION_SIMPLE } ;
CONDITION_SIMPLE = EXPRESSION, COMPARISON_OPERATOR, EXPRESSION ;
LOGICAL_OPERATOR = "e" | "ou" ;
COMPARISON_OPERATOR = "==" | "!-" | "<" | ">" ;

EXPRESSION = TERM, { ADD_OPERATOR, TERM } ;
TERM = FACTOR, { MULT_OPERATOR, FACTOR } ;
FACTOR = IDENTIFIER | NUMBER | STRING | FUNCTION_CALL | "(", EXPRESSION, ")" ;

ADD_OPERATOR = "+" | "-" ;
MULT_OPERATOR = "*" | "/" ;

IDENTIFIER = LETTER, { LETTER | DIGIT | "_" } ;
NUMBER = DIGIT, { DIGIT } ;
LETTER = "a" | "b" | ... | "z" | "A" | "B" | ... | "Z" ;
DIGIT = "0" | "1" | ... | "9" ;