bhuna.txt

Program     ::= {Statement}.
Block       ::= Statement | "{" {Statement} "}".
Statement   ::= (Definition | Assignment | Command | Control | Block) [";"].

Definition  ::= {"local" | "const"} Var "=" Expr<0>.        [[1]]
Assignment  ::= Var {LAccessor} "=" Expr<0>.
Command     ::= Var {LAccessor} Expr<0> {"," Expr<0>}.

Control     ::= "if" Expr<0> Block ["else" Block]
          | "while" Expr<0> Block
          .

Expr<N>     ::= Expr<N+1> {Op<N> Expr<N+1>}.
Expr<4>     ::= Primitive.

Op<0>       ::= "&" | "|".
Op<1>       ::= ">" | "<" | ">=" | "<=" | "=" | "!=".
Op<2>       ::= "+" | "-".
Op<3>       ::= "*" | "/" | "%".

Primitive   ::= "(" Expr<0> ")"
          | "!" Primitive
          | Var {RAccessor}
          | "^" {Var [","]} Block
          | "[" [Expr<0> {"," Expr<0>}] "]"
          | Literal
          .

Literal     ::= <<symbol>>                      [[3]]
          | <<number>>
          .

Var     ::= <<symbol>>.                     [[4]]

LAccessor   ::= "[" Expr<0> "]"
          | "." Literal
          .

RAccessor   ::= "[" Expr<0> "]"
          | "." Literal
          | "(" [Expr<0> {"," Expr<0>}] ")"
          .

Footnotes:

[[1]]:  Var must not itself be mentioned in the Expr<0>.
[[3]]:  Must start with lowercase letter.
[[4]]:  Must start with Uppercase letter.