/* FP */


identifier := "[A-Za-z_'$][A-Za-z0-9_'$]*"
number := "[0-9]+"
string := "\"(\\.|[^\"])+\""

whitespace := "[ \t\n\r]+|(#[^\n]*)"

program -> definition ...

definition -> "def" id = identifier "=" exp = expression : #sx(list (car id) exp)

expression -> exp1 exp1 ...

exp1 -> "while" exp2 exp1
     |  exp2 "->" exp2 [";" exp1]
     |  exp2

exp2 -> exp3 (operator1 exp2) ...
exp3 -> exp4 (operator2 exp3) ...
exp4 -> exp5 (operator3 exp4) ...
exp5 -> exp6 "." exp5
     |  exp6
exp6 -> value (operator4 exp6) ...

operator1 -> "&" | "|"
operator2 -> ">=" | "<=" | "==" | "!=" | ">" | "<"
operator3 -> "+" | "-"
operator4 -> "*" | "%"

value -> constant
      |  "def" ~
      |  identifier
      |  "/" value
      |  "\\" value
      |  "@" value
      |  "[" "]"
      |  "[" expression ("," expression) ... "]"
      |  "(" (operator1 | operator2 | operator3 | operator4) ")"
      |  "(" expression ")"

constant -> number
         |  string
         |  "<" constant ("," constant) ... ">"

start -> program