spread0.atg

一个Pascal语言分析器

COMPILER Spreadsheet
(* Grammar for a very simple spreadsheet *)

IGNORE CHR(9) .. CHR(13)
IGNORE CASE

COMMENTS FROM "(*" TO "*)"

CHARACTERS
  letter     = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz" .
  digit      = "0123456789" .

TOKENS
  identifier = letter .
  number     = digit { digit} .

PRODUCTIONS
  Spreadsheet = { Command } "QUIT" .
  Command     = [ Expression ]
                ("UP" | "DOWN" | "LEFT" | "RIGHT" | "HOME" | "GOTO" Cell |
                "ENTER" ) .
  Expression  = [ "+" | "-" ] Term { "+" Term | "-" Term } .
  Term        = Factor { "*" Factor | "/" Factor | "%" Factor } .
  Factor      = number | Cell | "(" Expression ")" .
  Cell        = identifier number .

END Spreadsheet.