%import common.WS
%import common.CPP_COMMENT
%import common.INT
%import common.WORD

%ignore WS
%ignore CPP_COMMENT

start: (LABEL | ainstr | cinstr)*

LABEL: "(" WORD ")"

ainstr: "@" SYMBOL

SYMBOL: WORD
      | INT
      | "R" "0".."15"
      | "SP"
      | "LCL"
      | "ARG"
      | "THIS"
      | "THAT"
      | "KBD"
      | "SCREEN"

cinstr: (DEST "=")? COMP (";" JUMP)?

// not satisfied with this; could it be cleaner?
DEST: "A" "D"? "M"?
    | "A"? "D" "M"?
    | "A"? "D"? "M"

JUMP: "JGT"
    | "JEQ"
    | "JGE"
    | "JLT"
    | "JNE"
    | "JLE"
    | "JMP"