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-The GFCC Grammar Format
-Aarne Ranta
-December 14, 2007
-
-Author's address:
-[``http://www.cs.chalmers.se/~aarne`` http://www.cs.chalmers.se/~aarne]
-
-% to compile: txt2tags -thtml --toc gfcc.txt
-
-History:
-- 14 Dec 2007: simpler, Lisp-like concrete syntax of GFCC
-- 5 Oct 2007: new, better structured GFCC with full expressive power
-- 19 Oct: translation of lincats, new figures on C++
-- 3 Oct 2006: first version
-
-
-==What is GFCC==
-
-GFCC is a low-level format for GF grammars. Its aim is to contain the minimum
-that is needed to process GF grammars at runtime. This minimality has three
-advantages:
-- compact grammar files and run-time objects
-- time and space efficient processing
-- simple definition of interpreters
-
-
-Thus we also want to call GFCC the **portable grammar format**.
-
-The idea is that all embedded GF applications use GFCC.
-The GF system would be primarily used as a compiler and as a grammar
-development tool.
-
-Since GFCC is implemented in BNFC, a parser of the format is readily
-available for C, C++, C#, Haskell, Java, and OCaml. Also an XML 
-representation can be generated in BNFC. A 
-[reference implementation ../]
-of linearization and some other functions has been written in Haskell.
-
-
-==GFCC vs. GFC==
-
-GFCC is aimed to replace GFC as the run-time grammar format. GFC was designed
-to be a run-time format, but also to
-support separate compilation of grammars, i.e.
-to store the results of compiling 
-individual GF modules. But this means that GFC has to contain extra information,
-such as type annotations, which is only needed in compilation and not at
-run-time. In particular, the pattern matching syntax and semantics of GFC is
-complex and therefore difficult to implement in new platforms.
-
-Actually, GFC is planned to be omitted also as the target format of
-separate compilation, where plain GF (type annotated and partially evaluated)
-will be used instead. GFC provides only marginal advantages as a target format
-compared with GF, and it is therefore just extra weight to carry around this
-format.
-
-The main differences of GFCC compared with GFC (and GF) can be 
-summarized as follows:
-- there are no modules, and therefore no qualified names
-- a GFCC grammar is multilingual, and consists of a common abstract syntax 
-  together with one concrete syntax per language
-- records and tables are replaced by arrays
-- record labels and parameter values are replaced by integers
-- record projection and table selection are replaced by array indexing
-- even though the format does support dependent types and higher-order abstract
-  syntax, there is no interpreted yet that does this
-
-
-
-Here is an example of a GF grammar, consisting of three modules, 
-as translated to GFCC. The representations are aligned; 
-thus they do not completely
-reflect the order of judgements in GFCC files, which have different orders of
-blocks of judgements, and alphabetical sorting.
-```  
-                                    grammar Ex(Eng,Swe);
-
-abstract Ex = {                     abstract {
-  cat                                 cat
-    S ; NP ; VP ;                      NP[]; S[]; VP[];
-  fun                                 fun
-    Pred : NP -> VP -> S ;             Pred=[(($ 0! 1),(($ 1! 0)!($ 0! 0)))];
-    She, They : NP ;                   She=[0,"she"];
-    Sleep : VP ;                       They=[1,"they"];
-                                       Sleep=[["sleeps","sleep"]];
-}                                     } ;
-                                    
-concrete Eng of Ex = {              concrete Eng {
-  lincat                             lincat
-    S  = {s : Str} ;                  S=[()];
-    NP = {s : Str ; n : Num} ;        NP=[1,()];
-    VP = {s : Num => Str} ;           VP=[[(),()]];
-  param
-    Num = Sg | Pl ;
-  lin                                lin
-    Pred np vp = {                    Pred=[(($ 0! 1),(($ 1! 0)!($ 0! 0)))];
-      s = np.s ++ vp.s ! np.n} ;      
-    She = {s = "she" ; n = Sg} ;      She=[0,"she"];
-    They = {s = "they" ; n = Pl} ;    They = [1, "they"];
-    Sleep = {s = table {              Sleep=[["sleeps","sleep"]];
-      Sg => "sleeps" ; 
-      Pl => "sleep"                   
-      }                               
-    } ;
-}                                   } ;
-
-concrete Swe of Ex = {              concrete Swe {
-  lincat                             lincat
-    S  = {s : Str} ;                  S=[()];
-    NP = {s : Str} ;                  NP=[()];
-    VP = {s : Str} ;                  VP=[()];
-  param
-    Num = Sg | Pl ;
-  lin                                lin
-    Pred np vp = {                    Pred = [(($0!0),($1!0))];
-      s = np.s ++ vp.s} ;
-    She = {s = "hon"} ;               She = ["hon"];
-    They = {s = "de"} ;               They = ["de"];
-    Sleep = {s = "sover"} ;           Sleep = ["sover"];
-}                                     } ;                                   
-```
-
-==The syntax of GFCC files==
-
-The complete BNFC grammar, from which  
-the rules in this section are taken, is in the file 
-[``GF/GFCC/GFCC.cf`` ../DataGFCC.cf].
-
-
-===Top level===
-
-A grammar has a header telling the name of the abstract syntax
-(often specifying an application domain), and the names of
-the concrete languages. The abstract syntax and the concrete
-syntaxes themselves follow.
-```
-  Grm. Grammar  ::= 
-    "grammar" CId "(" [CId] ")" ";" 
-    Abstract ";" 
-    [Concrete] ;
-
-  Abs. Abstract ::= 
-    "abstract" "{" 
-      "flags" [Flag] 
-      "fun"   [FunDef] 
-      "cat"   [CatDef] 
-    "}" ;
-
-  Cnc. Concrete ::= 
-    "concrete" CId "{" 
-      "flags"  [Flag] 
-      "lin"    [LinDef] 
-      "oper"   [LinDef] 
-      "lincat" [LinDef] 
-      "lindef" [LinDef] 
-      "printname" [LinDef]
-    "}" ;
-```
-This syntax organizes each module to a sequence of **fields**, such
-as flags, linearizations, operations, linearization types, etc.
-It is envisaged that particular applications can ignore some
-of the fields, typically so that earlier fields are more
-important than later ones.
-
-The judgement forms have the following syntax.
-```
-  Flg. Flag     ::= CId "=" String ;
-  Cat. CatDef   ::= CId "[" [Hypo] "]" ;
-  Fun. FunDef   ::= CId ":" Type "=" Exp ;
-  Lin. LinDef   ::= CId "=" Term ;
-```
-For the run-time system, the reference implementation in Haskell
-uses a structure that gives efficient look-up:
-```
-  data GFCC = GFCC {
-    absname   :: CId ,
-    cncnames  :: [CId] ,
-    abstract  :: Abstr ,
-    concretes :: Map CId Concr
-    }
-
-  data Abstr = Abstr {
-    aflags  :: Map CId String,     -- value of a flag
-    funs    :: Map CId (Type,Exp), -- type and def of a fun
-    cats    :: Map CId [Hypo],     -- context of a cat
-    catfuns :: Map CId [CId]       -- funs yielding a cat (redundant, for fast lookup)
-    }
-
-  data Concr = Concr {
-    flags   :: Map CId String, -- value of a flag
-    lins    :: Map CId Term,   -- lin of a fun
-    opers   :: Map CId Term,   -- oper generated by subex elim
-    lincats :: Map CId Term,   -- lin type of a cat
-    lindefs :: Map CId Term,   -- lin default of a cat
-    printnames :: Map CId Term -- printname of a cat or a fun
-    }
-```
-These definitions are from [``GF/GFCC/DataGFCC.hs`` ../DataGFCC.hs].
-
-Identifiers (``CId``) are like ``Ident`` in GF, except that
-the compiler produces constants prefixed with ``_`` in
-the common subterm elimination optimization.
-```
-  token CId (('_' | letter) (letter | digit | '\'' | '_')*) ;
-```
-
-
-===Abstract syntax===
-
-Types are first-order function types built from argument type
-contexts and value types.
-category symbols. Syntax trees (``Exp``) are
-rose trees with nodes consisting of a head (``Atom``) and
-bound variables (``CId``). 
-```
-  DTyp. Type  ::= "[" [Hypo] "]" CId [Exp] ;        
-  DTr.  Exp   ::= "[" "(" [CId] ")" Atom [Exp] "]" ;
-  Hyp.  Hypo  ::= CId ":" Type ;
-```
-The head Atom is either a function
-constant, a bound variable, or a metavariable, or a string, integer, or float
-literal.
-```
-  AC.   Atom  ::= CId ;
-  AS.   Atom  ::= String ;
-  AI.   Atom  ::= Integer ;
-  AF.   Atom  ::= Double ;
-  AM.   Atom  ::= "?" Integer ;
-```
-The context-free types and trees of the "old GFCC" are special
-cases, which can be defined as follows:
-```
-  Typ.  Type  ::= [CId] "->" CId
-  Typ args val = DTyp [Hyp (CId "_") arg | arg <- args] val
-
-  Tr.   Exp   ::= "(" CId [Exp] ")"
-  Tr fun exps  = DTr [] fun exps
-```
-To store semantic (``def``) definitions by cases, the following expression
-form is provided, but it is only meaningful in the last field of a function
-declaration in an abstract syntax:
-```
-  EEq. Exp      ::= "{" [Equation] "}" ;
-  Equ. Equation ::= [Exp] "->" Exp ;
-```
-Notice that expressions are used to encode patterns. Primitive notions
-(the default semantics in GF) are encoded as empty sets of equations
-(``[]``). For a constructor (canonical form) of a category ``C``, we
-aim to use the encoding as the application ``(_constr C)``.
-
-
-
-===Concrete syntax===
-
-Linearization terms (``Term``) are built as follows.
-Constructor names are shown to make the later code
-examples readable.
-```
-  R.  Term ::= "[" [Term] "]" ;        -- array (record/table)
-  P.  Term ::= "(" Term "!" Term ")" ; -- access to field (projection/selection)
-  S.  Term ::= "(" [Term] ")" ;        -- concatenated sequence
-  K.  Term ::= Tokn ;                  -- token
-  V.  Term ::= "$" Integer ;           -- argument (subtree)
-  C.  Term ::= Integer ;               -- array index (label/parameter value)
-  FV. Term ::= "[|" [Term] "|]" ;      -- free variation
-  TM. Term ::= "?" ;                   -- linearization of metavariable
-```
-Tokens are strings or (maybe obsolescent) prefix-dependent
-variant lists.
-```
-  KS.  Tokn     ::= String ;
-  KP.  Tokn     ::= "[" "pre" [String] "[" [Variant] "]" "]" ;
-  Var. Variant  ::= [String] "/" [String] ;
-```
-Two special forms of terms are introduced by the compiler
-as optimizations. They can in principle be eliminated, but
-their presence makes grammars much more compact. Their semantics
-will be explained in a later section.
-```
-  F.  Term ::= CId ;                     -- global constant
-  W.  Term ::= "(" String "+" Term ")" ; -- prefix + suffix table
-```
-There is also a deprecated form of "record parameter alias",
-```
-  RP. Term ::= "(" Term "@" Term ")";    -- DEPRECATED
-```
-which will be removed when the migration to new GFCC is complete.
-
-
-
-==The semantics of concrete syntax terms==
-
-The code in this section is from [``GF/GFCC/Linearize.hs`` ../Linearize.hs].
-
-
-===Linearization and realization===
-
-The linearization algorithm is essentially the same as in
-GFC: a tree is linearized by evaluating its linearization term
-in the environment of the linearizations of the subtrees.
-Literal atoms are linearized in the obvious way.
-The function also needs to know the language (i.e. concrete syntax)
-in which linearization is performed.
-```
-  linExp :: GFCC -> CId -> Exp -> Term
-  linExp gfcc lang tree@(DTr _ at trees) = case at of
-    AC fun -> comp (Prelude.map lin trees) $ look fun
-    AS s   -> R [kks (show s)] -- quoted
-    AI i   -> R [kks (show i)]
-    AF d   -> R [kks (show d)]
-    AM     -> TM
-   where
-     lin  = linExp gfcc lang
-     comp = compute gfcc lang
-     look = lookLin gfcc lang
-```
-TODO: bindings must be supported.
-
-The result of linearization is usually a record, which is realized as
-a string using the following algorithm.
-```
-  realize :: Term -> String
-  realize trm = case trm of
-    R (t:_)  -> realize t
-    S ss     -> unwords $ Prelude.map realize ss
-    K (KS s) -> s
-    K (KP s _) -> unwords s ---- prefix choice TODO
-    W s t    -> s ++ realize t
-    FV (t:_) -> realize t
-    TM       -> "?"
-```
-Notice that realization always picks the first field of a record.
-If a linearization type has more than one field, the first field
-does not necessarily contain the desired string.
-Also notice that the order of record fields in GFCC is not necessarily
-the same as in GF source.
-
-
-===Term evaluation===
-
-Evaluation follows call-by-value order, with two environments
-needed:
-- the grammar (a concrete syntax) to give the global constants
-- an array of terms to give the subtree linearizations
-
-
-The code is presented in one-level pattern matching, to
-enable reimplementations in languages that do not permit
-deep patterns (such as Java and C++).
-```
-compute :: GFCC -> CId -> [Term] -> Term -> Term
-compute gfcc lang args = comp where
-  comp trm = case trm of
-    P r p  -> proj (comp r) (comp p)
-    W s t  -> W s (comp t)
-    R ts   -> R $ Prelude.map comp ts
-    V i    -> idx args (fromInteger i)  -- already computed
-    F c    -> comp $ look c             -- not computed (if contains V)
-    FV ts  -> FV $ Prelude.map comp ts
-    S ts   -> S $ Prelude.filter (/= S []) $ Prelude.map comp ts
-    _ -> trm
-
-  look = lookOper gfcc lang
-
-  idx xs i = xs !! i
-
-  proj r p = case (r,p) of
-    (_,     FV ts) -> FV $ Prelude.map (proj r) ts
-    (FV ts, _    ) -> FV $ Prelude.map (\t -> proj t p) ts
-    (W s t, _)     -> kks (s ++ getString (proj t p))
-    _              -> comp $ getField r (getIndex p)
-
-  getString t = case t of
-    K (KS s) -> s
-    _ -> trace ("ERROR in grammar compiler: string from "++ show t) "ERR"
-
-  getIndex t =  case t of
-    C i    -> fromInteger i
-    RP p _ -> getIndex p
-    TM     -> 0  -- default value for parameter
-    _ -> trace ("ERROR in grammar compiler: index from " ++ show t) 0
-
-  getField t i = case t of
-    R rs   -> idx rs i
-    RP _ r -> getField r i
-    TM     -> TM
-    _ -> trace ("ERROR in grammar compiler: field from " ++ show t) t
-```
-
-===The special term constructors===
-
-The three forms introduced by the compiler may a need special
-explanation.
-
-Global constants
-```
-  Term ::= CId ;
-```
-are shorthands for complex terms. They are produced by the
-compiler by (iterated) **common subexpression elimination**.
-They are often more powerful than hand-devised code sharing in the source
-code. They could be computed off-line by replacing each identifier by 
-its definition.
-
-**Prefix-suffix tables**
-```
-  Term ::= "(" String "+" Term ")" ; 
-```
-represent tables of word forms divided to the longest common prefix
-and its array of suffixes. In the example grammar above, we have
-```
-  Sleep = [("sleep" + ["s",""])]
-```
-which in fact is equal to the array of full forms
-```
-  ["sleeps", "sleep"]
-```
-The power of this construction comes from the fact that suffix sets
-tend to be repeated in a language, and can therefore be collected
-by common subexpression elimination. It is this technique that
-explains the used syntax rather than the more accurate
-```
-  "(" String "+" [String] ")"
-```
-since we want the suffix part to be a ``Term`` for the optimization to
-take effect.
-
-
-
-==Compiling to GFCC==
-
-Compilation to GFCC is performed by the GF grammar compiler, and
-GFCC interpreters need not know what it does. For grammar writers,
-however, it might be interesting to know what happens to the grammars
-in the process.
-
-The compilation phases are the following
-+ type check and partially evaluate GF source
-+ create a symbol table mapping the GF parameter and record types to
-  fixed-size arrays, and parameter values and record labels to integers
-+ traverse the linearization rules replacing parameters and labels by integers
-+ reorganize the created GF grammar so that it has just one abstract syntax
-  and one concrete syntax per language
-+ TODO: apply UTF8 encoding to the grammar, if not yet applied (this is told by the
-  ``coding`` flag)
-+ translate the GF grammar object to a GFCC grammar object, using a simple
-  compositional mapping
-+ perform the word-suffix optimization on GFCC linearization terms
-+ perform subexpression elimination on each concrete syntax module
-+ print out the GFCC code
-
-
-
-
-===Problems in GFCC compilation===
-
-Two major problems had to be solved in compiling GF to GFCC:
-- consistent order of tables and records, to permit the array translation
-- run-time variables in complex parameter values.
-
-
-The current implementation is still experimental and may fail
-to generate correct code. Any errors remaining are likely to be 
-related to the two problems just mentioned.
-
-The order problem is solved in slightly different ways for tables and records.
-In both cases, **eta expansion** is used to establish a
-canonical order. Tables are ordered by applying the preorder induced
-by ``param`` definitions. Records are ordered by sorting them by labels.
-This means that
-e.g. the ``s`` field will in general no longer appear as the first
-field, even if it does so in the GF source code. But relying on the
-order of fields in a labelled record would be misplaced anyway.
-
-The canonical form of records is further complicated by lock fields,
-i.e. dummy fields of form ``lock_C = <>``, which are added to grammar
-libraries to force intensionality of linearization types. The problem
-is that the absence of a lock field only generates a warning, not
-an error. Therefore a GF grammar can contain objects of the same
-type with and without a lock field. This problem was solved in GFCC
-generation by just removing all lock fields (defined as fields whose
-type is the empty record type). This has the further advantage of
-(slightly) reducing the grammar size. More importantly, it is safe
-to remove lock fields, because they are never used in computation,
-and because intensional types are only needed in grammars reused
-as libraries, not in grammars used at runtime.
-
-While the order problem is rather bureaucratic in nature, run-time 
-variables are an interesting problem. They arise in the presence
-of complex parameter values, created by argument-taking constructors
-and parameter records. To give an example, consider the GF parameter
-type system
-```
-  Number = Sg | Pl ;
-  Person = P1 | P2 | P3 ;
-  Agr = Ag Number Person ;
-```
-The values can be translated to integers in the expected way,
-```
-  Sg = 0, Pl = 1
-  P1 = 0, P2 = 1, P3 = 2
-  Ag Sg P1 = 0, Ag Sg P2 = 1, Ag Sg P3 = 2,
-  Ag Pl P1 = 3, Ag Pl P2 = 4, Ag Pl P3 = 5
-```
-However, an argument of ``Agr`` can be a run-time variable, as in
-```
-  Ag np.n P3
-```
-This expression must first be translated to a case expression,
-```
-  case np.n of {
-    0 => 2 ;
-    1 => 5
-    }
-```
-which can then be translated to the GFCC term
-```
-  ([2,5] ! ($0 ! $1))  
-```
-assuming that the variable ``np`` is the first argument and that its
-``Number`` field is the second in the record.
-
-This transformation of course has to be performed recursively, since
-there can be several run-time variables in a parameter value:
-```
-  Ag np.n np.p
-```
-A similar transformation would be possible to deal with the double
-role of parameter records discussed above. Thus the type
-```
-  RNP = {n : Number ; p : Person}
-```
-could be uniformly translated into the set ``{0,1,2,3,4,5}``
-as ``Agr`` above. Selections would be simple instances of indexing.
-But any projection from the record should be translated into
-a case expression,
-```
-  rnp.n  ===> 
-  case rnp of {
-    0 => 0 ;
-    1 => 0 ;
-    2 => 0 ;
-    3 => 1 ;
-    4 => 1 ;
-    5 => 1
-    }
-```
-To avoid the code bloat resulting from this, we have chosen to
-deal with records by a **currying** transformation:
-```
-  table {n : Number ; p : Person} {... ...}
-   ===>
-  table Number {Sg => table Person {...} ; table Person {...}}
-```
-This is performed when GFCC is generated. Selections with
-records have to be treated likewise,
-```
-  t ! r   ===> t ! r.n ! r.p
-```
-
-
-===The representation of linearization types===
-
-Linearization types (``lincat``) are not needed when generating with
-GFCC, but they have been added to enable parser generation directly from
-GFCC. The linearization type definitions are shown as a part of the
-concrete syntax, by using terms to represent types. Here is the table
-showing how different linearization types are encoded.
-```
-  P*                         = max(P)         -- parameter type
-  {r1 : T1 ; ... ; rn : Tn}* = [T1*,...,Tn*]  -- record
-  (P => T)*                  = [T* ,...,T*]   -- table, size(P) cases
-  Str*                       = ()
-```
-For example, the linearization type ``present/CatEng.NP`` is
-translated as follows:
-```
-  NP = {
-    a : {                     -- 6 = 2*3 values
-      n : {ParamX.Number} ;   -- 2 values
-      p : {ParamX.Person}     -- 3 values
-    } ;
-    s : {ResEng.Case} => Str  -- 3 values
-  }
-
-  __NP = [[1,2],[(),(),()]]
-```
-
-
-
-
-===Running the compiler and the GFCC interpreter===
-
-GFCC generation is a part of the 
-[developers' version http://www.cs.chalmers.se/Cs/Research/Language-technology/darcs/GF/doc/darcs.html] 
-of GF since September 2006. To invoke the compiler, the flag 
-``-printer=gfcc`` to the command
-``pm = print_multi`` is used. It is wise to recompile the grammar from
-source, since previously compiled libraries may not obey the canonical
-order of records. 
-Here is an example, performed in
-[example/bronzeage ../../../../../examples/bronzeage].
-```
-  i -src -path=.:prelude:resource-1.0/* -optimize=all_subs BronzeageEng.gf
-  i -src -path=.:prelude:resource-1.0/* -optimize=all_subs BronzeageGer.gf
-  strip
-  pm -printer=gfcc | wf bronze.gfcc
-```
-There is also an experimental batch compiler, which does not use the GFC
-format or the record aliases. It can be produced by
-```
-  make gfc
-```
-in ``GF/src``, and invoked by
-```
-  gfc --make FILES
-```
-
-
-
-
-==The reference interpreter==
-
-The reference interpreter written in Haskell consists of the following files:
-```
-  -- source file for BNFC
-  GFCC.cf       -- labelled BNF grammar of gfcc
-
-  -- files generated by BNFC
-  AbsGFCC.hs    -- abstrac syntax datatypes
-  ErrM.hs       -- error monad used internally
-  LexGFCC.hs    -- lexer of gfcc files
-  ParGFCC.hs    -- parser of gfcc files and syntax trees
-  PrintGFCC.hs  -- printer of gfcc files and syntax trees
-
-  -- hand-written files
-  DataGFCC.hs   -- grammar datatype, post-parser grammar creation
-  Linearize.hs  -- linearization and evaluation
-  Macros.hs     -- utilities abstracting away from GFCC datatypes
-  Generate.hs   -- random and exhaustive generation, generate-and-test parsing
-  API.hs        -- functionalities accessible in embedded GF applications
-  Generate.hs   -- random and exhaustive generation
-  Shell.hs      -- main function - a simple command interpreter
-```
-It is included in the
-[developers' version http://www.cs.chalmers.se/Cs/Research/Language-technology/darcs/GF/doc/darcs.html]
-of GF, in the subdirectories [``GF/src/GF/GFCC`` ../] and 
-[``GF/src/GF/Devel`` ../../Devel].
-
-As of September 2007, default parsing in main GF uses GFCC (implemented by Krasimir
-Angelov). The interpreter uses the relevant modules
-```
-  GF/Conversions/SimpleToFCFG.hs  -- generate parser from GFCC
-  GF/Parsing/FCFG.hs              -- run the parser
-```
-
-
-To compile the interpreter, type
-```
-  make gfcc
-```
-in ``GF/src``. To run it, type
-```
-  ./gfcc <GFCC-file>
-```
-The available commands are
-- ``gr <Cat> <Int>``:  generate a number of random trees in category.
-  and show their linearizations in all languages
-- ``grt <Cat> <Int>``:  generate a number of random trees in category.
-  and show the trees and their linearizations in all languages
-- ``gt <Cat> <Int>``:  generate a number of trees in category from smallest,
-  and show their linearizations in all languages
-- ``gtt <Cat> <Int>``:  generate a number of trees in category from smallest,
-  and show the trees and their linearizations in all languages
-- ``p <Lang> <Cat> <String>``: parse a string into a set of trees
-- ``lin <Tree>``: linearize tree in all languages, also showing full records
-- ``q``: terminate the system cleanly
-
-
-
-==Embedded formats==
-
-- JavaScript: compiler of linearization and abstract syntax
-
-- Haskell: compiler of abstract syntax and interpreter with parsing,
-  linearization, and generation
-
-- C: compiler of linearization (old GFCC)
-
-- C++: embedded interpreter supporting linearization (old GFCC)
-
-
-
-==Some things to do==
-
-Support for dependent types, higher-order abstract syntax, and
-semantic definition in GFCC generation and interpreters.
-
-Replacing the entire GF shell by one based on GFCC.
-
-Interpreter in Java.
-
-Hand-written parsers for GFCC grammars to reduce code size
-(and efficiency?) of interpreters.
-
-Binary format and/or file compression of GFCC output.
-
-Syntax editor based on GFCC.
-
-Rewriting of resource libraries in order to exploit the
-word-suffix sharing better (depth-one tables, as in FM).
-