smlyacc generates a file $\mathrm{⟨}$YaccInputFile$\mathrm{⟩}$.grm.sml containing one structure of the following signature.

    signature ML_LRVALS =
      sig
         structure Tokens : ML_TOKENS
         structure Parser : PARSER
         sharing type Parser.token = Tokens.token
      end

This signature and other supporting library for smlyacc are collected in smlyacc-lib.smi. In order to use the generated parser program file, the following interface file must be written.

    _require "basis.smi"
    _require "ml-yacc-lib.smi"

    structure <Name> =
    struct
      structure Parser =
      struct
        type token (= boxed)
        type stream (= boxed)
        type result = Absyn.parseresult
        type pos = int
        type arg = unit
        exception ParseError
        val makeStream : {lexer:unit -> token} -> stream
        val consStream : token * stream -> stream
        val getStream : stream -> token * stream
        val sameToken : token * token -> bool
        val parse : {lookahead:int,
                     stream:stream,
                     error: (string * pos * pos -> unit),
                     arg: arg}
                    -> result * stream
      end
      structure Tokens =
      struct
        type pos = Parser.pos
        type token = Parser.token
        <the set of Token forming functions>
         ...
        val EOF: word *  pos * pos -> token
        val CHAR: string *  pos * pos -> token
        ....
      end
    end

In Parser structure, pos，arg， result types are those that are specified in $⟨YaccInputFileName⟩$.grm. The other components are fixed and should be specified as above. To write the Token structure，copy the contents of the $⟨YaccInputFileName⟩$.grm.sig signature generated by smlyacc.

The components are described below.

• •

  token type. The abstract type for the token returned by the lexer generated by smllex.

• •

  stream type. The abstract type for the input stream of the parser.

• •

  result type. The type of the output of the parser. It should be the same as the type of the attribute of the top-level grammar rule specified in the $\mathrm{⟨}$YaccInputFile$\mathrm{⟩}$.grm file. の属の性の型と同一である．

• •

  pos type. The position data type used by the lexer.

• •

  arg type. The additional argument type for the parser specified in the $\mathrm{⟨}$YaccInputFile$\mathrm{⟩}$.grm file.

• •

  ParseError exception. Parse error exception generated by the parser.

• •

  makeStream function. It takes a lexer and return the input stream for the parser.

• •

  consStream function. This up-push one token to the given input stream.

• •

  getStream function. It returns the first token in the current input stream.

• •

  sameToken function. Token equality checking function.

• •

  parse function. The parser function. It takes the current input stream and returns the generated abstract syntax tree and the rest of the input stream.