(* Грамматика арифметического калькулятора *)

expression = term , { ( "+" | "-" ) , term } ;
term       = factor , { ( "*" | "/" ) , factor } ;
factor     = [ "-" ] , ( primary | function ) ;
function   = ( "sin" | "cos" ) , "(" , expression , ")" ;
primary    = number | "(" , expression , ")" ;
number     = digit , { digit } , [ "." , digit , { digit } ] ;
digit      = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" ;