%{
open LDText.Ast
// helper functions
%}

// start token
%start start

// tokens, used by lexer
%token <string> IDENTIFIER
%token LEFT_PAREN
%token RIGHT_PAREN
%token LEFT_BRACKET
%token RIGHT_BRACKET
%token COMMA
%token SEMICOLON
%token QUESTION_MARK
%token EOF

// return type of parser, marked by start token
%type <Rung option> rung

%%

start:
  | instr EOF { $1 }

instr:
  | IDENTIFIER LEFT_PAREN operands RIGHT_PAREN { StepInstr { Op = $1; Args = [ $3 ] } }

operands:
  | { }
  | operand operands { $1; $2 }

operand:
  | IDENTIFIER { OperandTag $1 }
  | QUESTION_MARK { OperandHole }
%%