As Fix 2 ME

AsFix2ME is a more compact variant of AsFix2^?. See the AsFix topic for a general overview of AsFix. This topic describes the difference between AsFix2 and AsFix2ME in more detail.

Literals in AsFix2ME

Consider the syntax definition

---

  definition
  module Exp
  exports
    sorts Exp
    context-free syntax
      "nil" -> Exp

    lexical syntax
      [\t\n\r\ ] -> LAYOUT

---

Representation in AsFix2ME:

---

  appl(
    prod([lit("nil")], cf(sort("Exp")), no-attrs)
  , [lit("nil")]
  )

---

Representation in AsFix2:

---

  appl(
    prod([lit("nil")], cf(sort("Exp")), no-attrs)
  , [ appl(
        prod(
          [char-class([110]), char-class([105]), char-class([108])]
        , lit("nil")
        , no-attrs
        )
      , [110, 105, 108]
      )
    ]
  )

---

Layout in AsFix2ME

Lexical syntax in AsFix2ME

Consider the syntax definition

---

  definition
  module Exp
  hiddens
    sorts IntConst

  exports
    sorts Exp
  
    lexical syntax
      [\ \t\n]  -> LAYOUT
      [0-9]+    -> IntConst
  
    context-free syntax
      IntConst  -> Exp {cons("Int")}

---

Producing a parse table:

  sdf2table -i Exp-tiny.def.def -o Exp-tiny.tbl -m Exp

Stratego Script to extract the tree related to the context-free symbol IntConst:

  import simple-traversal ;;
  oncetd(?appl(prod(_, cf(sort("IntConst")), _), _); ?x) ;;
  !x ;;

Parse the expression "12" to AsFix2^?

echo "1" | sglr -2 -p Exp-tiny.tbl | stratego-shell --script extract-lex.srts | pp-aterm

---

appl(
  prod(
    [lex(sort("IntConst"))]
  , cf(sort("IntConst"))
  , no-attrs
  )
, [ appl(
      prod(
        [lex(iter(char-class([range(48, 57)])))]
      , lex(sort("IntConst"))
      , no-attrs
      )
    , [ appl(
          prod(
            [ lex(iter(char-class([range(48, 57)])))
            , lex(iter(char-class([range(48, 57)])))
            ]
          , lex(iter(char-class([range(48, 57)])))
          , attrs([assoc(left)])
          )
        , [ appl(
              prod(
                [char-class([range(48, 57)])]
              , lex(iter(char-class([range(48, 57)])))
              , no-attrs
              )
            , [49]
            )
          , appl(
              prod(
                [char-class([range(48, 57)])]
              , lex(iter(char-class([range(48, 57)])))
              , no-attrs
              )
            , [50]
            )
          ]
        )
      ]
    )
  ]
)

---

Parsing the same expression to AsFix2ME:

  echo "12" | sglr -m -p Exp-tiny.tbl | stratego-shell --script extract-cf.strs | pp-aterm

---

appl(
  prod(
    [lex(sort("IntConst"))]
  , cf(sort("IntConst"))
  , no-attrs
  )
, [ appl(
      list(iter-star(char-class([range(0, 255)])))
    , [49, 50]
    )
  ]
)

---

• Note: If we add a constructor to the IntConst production the constructor name will be lost.

Now consider the syntax definition:

---

  definition
  module Exp
  hiddens
    sorts DecConst

  exports
    sorts Exp
  
    lexical syntax
      [\ \t\n]  -> LAYOUT
      [0-9]+ "." [0-9]+ -> DecConst {cons("DecConst")}
  
    context-free syntax
      DecConst  -> Exp

---

Parsing to AsFix2ME:

  echo "13.25" | sglr -m -p Exp-tiny.tbl | stratego-shell --script extract-cf.strs | pp-aterm

---

appl(
  prod(
    [lex(sort("DecConst"))]
  , cf(sort("DecConst"))
  , no-attrs
  )
, [ appl(
      list(iter-star(char-class([range(0, 255)])))
    , [49, 51, 46, 50, 53]
    )
  ]
)

---

Syntax in AsFix2ME

Consider the syntax definition

---

  definition
  module Exp
  hiddens
    sorts DecConst

  exports
    sorts Exp
    context-free syntax
      DecConst  -> Exp

    syntax
      [0-9]+ "." [0-9]+ -> DecConst {cons("DecConst")}
      DecConst -> <DecConst-CF>

    lexical syntax
      [\t\n\r\ ] -> LAYOUT

---

In this case the DecConst application is represented as a tree in AsFix2ME, just like in AsFix2.