#lang brag
u-program: [/NEWLINE+] (u-expr [/NEWLINE+])*
u-expr:
     ; u-series ; string series
      | u-atom
      | u-converting-num
      | u-sexp
u-sexp:
      /L_PAREN u-expr (/SEPERATOR u-expr)* /R_PAREN
u-series: (u-atom | u-sexp)+
~~~u-converting-num: /NUM_CONVERTER (u-id | u-number)
~~~u-atom: u-id | u-string | u-number | (NEWLINE+)
~~~u-number: INTEGER | DECIMAL
u-id: ID
@u-string: u-char+
@u-char: CHAR | " "