From 51ac00a9872c92b38676356ec116446b2ef7ebf0 Mon Sep 17 00:00:00 2001 From: aarne Date: Fri, 5 Oct 2007 16:18:23 +0000 Subject: documented new GFCC --- src/GF/GFCC/doc/gfcc.html | 555 ++++++++++++++++++++++------------------------ 1 file changed, 261 insertions(+), 294 deletions(-) (limited to 'src/GF/GFCC/doc/gfcc.html') diff --git a/src/GF/GFCC/doc/gfcc.html b/src/GF/GFCC/doc/gfcc.html index c43188e9f..8f8c478c0 100644 --- a/src/GF/GFCC/doc/gfcc.html +++ b/src/GF/GFCC/doc/gfcc.html @@ -7,41 +7,9 @@

The GFCC Grammar Format

Aarne Ranta
-October 19, 2006 +October 5, 2007
-

-
-

- - -

-
-

Author's address: http://www.cs.chalmers.se/~aarne @@ -50,11 +18,11 @@ Author's address: History:

-

What is GFCC

GFCC is a low-level format for GF grammars. Its aim is to contain the minimum @@ -68,18 +36,20 @@ advantages:

-The idea is that all embedded GF applications are compiled to GFCC. +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++, Haskell, Java, and OCaml. Also an XML -representation is generated in BNFC. A +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 @@ -92,7 +62,14 @@ run-time. In particular, the pattern matching syntax and semantics of GFC is complex and therefore difficult to implement in new platforms.

-The main differences of GFCC compared with GFC can be summarized as follows: +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:

Here is an example of a GF grammar, consisting of three modules, -as translated to GFCC. The representations are aligned, with the exceptions -due to the alphabetical sorting of GFCC grammars. +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 
-      S ; NP ; VP ;
-    fun 
-      Pred : NP -> VP -> S ;            Pred : NP,VP -> S = (Pred);
-      She, They : NP ;                  She : -> NP = (She);
-      Sleep : VP ;                      Sleep : -> VP = (Sleep); 
-                                        They : -> NP = (They);
+    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
-      S  = {s : Str} ;
-      NP = {s : Str ; n : Num} ;
-      VP = {s : Num => Str} ;
+    lincat                             lincat
+      S  = {s : Str} ;                  S=[()];
+      NP = {s : Str ; n : Num} ;        NP=[1,()];
+      VP = {s : Num => Str} ;           VP=[[(),()]];
     param
       Num = Sg | Pl ;
-    lin
-      Pred np vp = {                    Pred = [(($0!1),(($1!0)!($0!0)))];
+    lin                                lin
+      Pred np vp = {                    Pred=[(($ 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} ;    
-      Sleep = {s = table {              Sleep = [("sleep" + ["s",""])];
+      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"                   They = [1, "they"];
-        }                               } ;
+        Pl => "sleep"                   
+        }                               
       } ;
-  }
+  }                                   } ;
   
   concrete Swe of Ex = {              concrete Swe {
-    lincat
-      S  = {s : Str} ;
-      NP = {s : Str} ;
-      VP = {s : Str} ;
+    lincat                             lincat
+      S  = {s : Str} ;                  S=[()];
+      NP = {s : Str} ;                  NP=[()];
+      VP = {s : Str} ;                  VP=[()];
     param
       Num = Sg | Pl ;
-    lin
+    lin                                lin
       Pred np vp = {                    Pred = [(($0!0),($1!0))];
         s = np.s ++ vp.s} ;
       She = {s = "hon"} ;               She = ["hon"];
@@ -159,9 +136,12 @@ due to the alphabetical sorting of GFCC grammars.
   }                                     } ;

-

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. +

Top level

A grammar has a header telling the name of the abstract syntax @@ -170,25 +150,43 @@ the concrete languages. The abstract syntax and the concrete syntaxes themselves follow. 

-    Grammar  ::= Header ";" Abstract ";" [Concrete] ;
-    Header   ::= "grammar" CId "(" [CId] ")" ;
-    Abstract ::= "abstract" "{" [AbsDef] "}" ;
-    Concrete ::= "concrete" CId "{" [CncDef] "}" ;
+    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]
+      "}" ;

-Abstract syntax judgements give typings and semantic definitions. -Concrete syntax judgements give linearizations. +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.

-
-    AbsDef   ::= CId ":" Type "=" Exp ;
-    CncDef   ::= CId "=" Term ;
-

-Also flags are possible, local to each "module" (i.e. abstract and concretes). +The judgement forms have the following syntax. 

-    AbsDef   ::= "%" CId "=" String ;
-    CncDef   ::= "%" CId "=" String ;
+    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 @@ -203,33 +201,84 @@ uses a structure that gives efficient look-up: } data Abstr = Abstr { - funs :: Map CId Type, -- find the type of a fun - cats :: Map CId [CId] -- find the funs giving a cat + 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) } - type Concr = Map CId Term + 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. +

+

+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 +Types are first-order function types built from argument type +contexts and value types. category symbols. Syntax trees (Exp) are -rose trees with the head (Atom) either a function -constant, a metavariable, or a string, integer, or float +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. 

-    Type     ::= [CId] "->" CId ;
-    Exp      ::= "(" Atom [Exp] ")" ;
-    Atom     ::= CId ;        -- function constant
-    Atom     ::= "?" ;        -- metavariable
-    Atom     ::= String ;     -- string literal
-    Atom     ::= Integer ;    -- integer literal
-    Atom     ::= Double ;     -- 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. @@ -237,12 +286,12 @@ Constructor names are shown to make the later code examples readable. 

-    R.  Term ::= "[" [Term] "]" ;        -- array
-    P.  Term ::= "(" Term "!" Term ")" ; -- access to indexed field
-    S.  Term ::= "(" [Term] ")" ;        -- sequence with ++
+    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 ::= "$" Integer ;           -- argument
-    C.  Term ::= Integer ;               -- array index
+    V.  Term ::= "$" Integer ;           -- argument (subtree)
+    C.  Term ::= Integer ;               -- array index (label/parameter value)
     FV. Term ::= "[|" [Term] "|]" ;      -- free variation
     TM. Term ::= "?" ;                   -- linearization of metavariable
@@ -256,7 +305,7 @@ variant lists. Var. Variant ::= [String] "/" [String] ;

-Three special forms of terms are introduced by the compiler +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. @@ -264,20 +313,20 @@ will be explained in a later section. 

     F.  Term ::= CId ;                     -- global constant
     W.  Term ::= "(" String "+" Term ")" ; -- prefix + suffix table
-    RP. Term ::= "(" Term "@" Term ")";    -- record parameter alias

-Identifiers are like Ident in GF and GFC, except that -the compiler produces constants prefixed with _ in -the common subterm elimination optimization. +There is also a deprecated form of "record parameter alias", 

-    token CId (('_' | letter) (letter | digit | '\'' | '_')*) ;
+    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. +

Linearization and realization

The linearization algorithm is essentially the same as in @@ -289,18 +338,21 @@ in which linearization is performed. 

     linExp :: GFCC -> CId -> Exp -> Term
-    linExp mcfg lang tree@(Tr at trees) = case at of
+    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 mcfg lang
-       comp = compute mcfg lang
-       look = lookLin mcfg lang
+       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.

@@ -316,12 +368,12 @@ a string using the following algorithm. TM -> "?"

-Since the order of record fields is not necessarily -the same as in GF source, -this realization does not work securely for -categories whose lincats more than one field. +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 @@ -339,10 +391,9 @@ deep patterns (such as Java and C++). 

   compute :: GFCC -> CId -> [Term] -> Term -> Term
-  compute mcfg lang args = comp where
+  compute gfcc lang args = comp where
     comp trm = case trm of
       P r p  -> proj (comp r) (comp p)
-      RP i t -> RP (comp i) (comp t)
       W s t  -> W s (comp t)
       R ts   -> R $ Prelude.map comp ts
       V i    -> idx args (fromInteger i)  -- already computed
@@ -351,7 +402,7 @@ deep patterns (such as Java and C++).
       S ts   -> S $ Prelude.filter (/= S []) $ Prelude.map comp ts
       _ -> trm
   
-    look = lookLin mcfg lang
+    look = lookOper gfcc lang
   
     idx xs i = xs !! i
   
@@ -377,7 +428,6 @@ deep patterns (such as Java and C++).
       _ -> 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 @@ -391,13 +441,13 @@ Global constants

are shorthands for complex terms. They are produced by the -compiler by (iterated) common subexpression elimination. +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 +Prefix-suffix tables 

     Term ::= "(" String "+" Term ")" ; 
@@ -428,56 +478,6 @@ explains the used syntax rather than the more accurate
 since we want the suffix part to be a Term for the optimization to
 take effect.
 

-

-The most curious construct of GFCC is the parameter array alias, 
-

-
-    Term ::= "(" Term "@" Term ")";
-

-

-This form is used as the value of parameter records, such as the type
-

-
-    {n : Number ; p : Person}
-

-

-The problem with parameter records is their double role.
-They can be used like parameter values, as indices in selection,
-

-
-    VP.s ! {n = Sg ; p = P3}
-

-

-but also as records, from which parameters can be projected:
-

-
-    {n = Sg ; p = P3}.n
-

-

-Whichever use is selected as primary, a prohibitively complex
-case expression must be generated at compilation to GFCC to get the
-other use. The adopted
-solution is to generate a pair containing both a parameter value index 
-and an array of indices of record fields. For instance, if we have
-

-
-    param Number = Sg | Pl ; Person = P1 | P2 | P3 ;
-

-

-we get the encoding
-

-
-    {n = Sg ; p = P3}  ---> (2 @ [0,2])
-

-

-The GFCC computation rules are essentially
-

-
-    (t ! (i @ _)) = (t ! i)
-    ((_ @ r) ! j)  =(r ! j)
-

-

-
 
Compiling to GFCC

 

 Compilation to GFCC is performed by the GF grammar compiler, and
@@ -489,32 +489,24 @@ in the process.
 The compilation phases are the following
 

 
    
-
  1. translate GF source to GFC, as always in GF
-
  2. undo GFC back-end optimizations
-
  3. perform the values optimization to normalize tables
-
  4. create a symbol table mapping the GFC parameter and record types to
+
  5. type check and partially evaluate GF source
+
  6. create a symbol table mapping the GF parameter and record types to
   fixed-size arrays, and parameter values and record labels to integers
 
  7. traverse the linearization rules replacing parameters and labels by integers
-
  8. reorganize the created GFC grammar so that it has just one abstract syntax
+
  9. reorganize the created GF grammar so that it has just one abstract syntax
   and one concrete syntax per language
-
  10. apply UTF8 encoding to the grammar, if not yet applied (this is told by the
+
  11. TODO: apply UTF8 encoding to the grammar, if not yet applied (this is told by the
   coding flag)
-
  12. translate the GFC syntax tree to a GFCC syntax tree, using a simple
+
  13. translate the GF grammar object to a GFCC grammar object, using a simple
   compositional mapping
 
  14. perform the word-suffix optimization on GFCC linearization terms
 
  15. perform subexpression elimination on each concrete syntax module
 
  16. print out the GFCC code
 

 
-

-Notice that a major part of the compilation is done within GFC, so that
-GFC-related tasks (such as parser generation) could be performed by
-using the old algorithms.
-

-
 
Problems in GFCC compilation

 

-Two major problems had to be solved in compiling GFC to GFCC:
+Two major problems had to be solved in compiling GF to GFCC:

-To avoid the code bloat resulting from this, we chose the alias representation -which is easy enough to deal with in interpreters. +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 @@ -647,14 +645,12 @@ concrete syntax, by using terms to represent types. Here is the table showing how different linearization types are encoded. 

-    P*                         = size(P)        -- parameter type              
-    {_ : I ; __ : R}*          = (I* @ R*)      -- record of parameters
-    {r1 : T1 ; ... ; rn : Tn}* = [T1*,...,Tn*]  -- other record
-    (P => T)*                  = [T* ,...,T*]   -- size(P) times
+    P*                         = max(P)         -- parameter type
+    {r1 : T1 ; ... ; rn : Tn}* = [T1*,...,Tn*]  -- record
+    (P => T)*                  = [T* ,...,T*]   -- table, size(P) cases
     Str*                       = ()

-The category symbols are prefixed with two underscores (__). For example, the linearization type present/CatEng.NP is translated as follows:

@@ -667,10 +663,9 @@ translated as follows: s : {ResEng.Case} => Str -- 3 values } - __NP = [(6@[2,3]),[(),(),()]] + __NP = [[1,2],[(),(),()]]

-

Running the compiler and the GFCC interpreter

GFCC generation is a part of the @@ -679,8 +674,7 @@ 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. To strip the grammar before -GFCC translation removes unnecessary interface references. +order of records. Here is an example, performed in example/bronzeage.

@@ -690,8 +684,20 @@ Here is an example, performed in 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: @@ -701,22 +707,36 @@ The reference interpreter written in Haskell consists of the following files: GFCC.cf -- labelled BNF grammar of gfcc -- files generated by BNFC - AbsGFCC.hs -- abstrac syntax of gfcc + 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 -- post-parser grammar creation, linearization and evaluation - GenGFCC.hs -- random and exhaustive generation, generate-and-test parsing - RunGFCC.hs -- main function - a simple command interpreter + 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 -of GF, in the subdirectory GF/src/GF/Canon/GFCC. +of GF, in the subdirectories GF/src/GF/GFCC and +GF/src/GF/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

@@ -741,87 +761,34 @@ The available commands are 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 <Int> <Cat> <String>: "parse", i.e. generate trees until match or - until the given number have been generated -
  • <Tree>: linearize tree in all languages, also showing full records -
  • quit: terminate the system cleanly +
  • 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 - -

    Interpreter in C++

    -

    -A base-line interpreter in C++ has been started. -Its main functionality is random generation of trees and linearization of them. -

    -

    -Here are some results from running the different interpreters, compared -to running the same grammar in GF, saved in .gfcm format. -The grammar contains the English, German, and Norwegian -versions of Bronzeage. The experiment was carried out on -Ubuntu Linux laptop with 1.5 GHz Intel centrino processor. -

    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    GFgfcc(hs)gfcc++
    program size7249k803k113k
    grammar size336k119k119k
    read grammar1150ms510ms100ms
    generate 2229500ms450ms800ms
    memory21M10M20M
    - -

    -

    -To summarize: -

    +

    Embedded formats

    -

    Some things to do

    -Interpreter in Java. +Support for dependent types, higher-order abstract syntax, and +semantic definition in GFCC generation and interpreters.

    -Parsing via MCFG +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. @@ -838,5 +805,5 @@ word-suffix sharing better (depth-one tables, as in FM).

    - + -- cgit v1.2.3