# Grammatical Framework History of Changes

Changes in functionality since May 17, 2005, release of GF Version 2.2

1/12 (BB,AR) The command `at = apply_transfer`, which applies a transfer function to a term. This is used for noncompositional translation. Transfer functions are defined in a special transfer language (file suffix `.tr`), which is compiled into a run-time transfer core language (file suffix `.trc`). The compiler is included in `GF/transfer`. The following is a complete example of how to try out transfer:

      % cd GF/transfer
      % make                            -- compile the trc compiler
      % cd examples                     -- GF/transfer/examples
      % ../compile_to_core -i../lib numerals.tr
      % mv numerals.trc ../../examples/numerals
      % cd ../../examples/numerals      -- GF/examples/numerals
      % gf
         > i decimal.gf
         > i BinaryDigits.gf
         > i numerals.trc
         > p -lang=Cncdecimal "123" | at num2bin | l
         1 0 0 1 1 0 0 1 1 1 0

Other relevant commands are:

- `i file.trc`: import a transfer module
- `pg -printer=transfer`: create a syntax datatype in `.tr` format

For more information on the commands, see `help`. Documentation on the transfer language: to appear.

17/11 (AR) Made it possible for lexers to be nondeterministic. Now with a simple-minded implementation that the parser is sent each lexing result in turn. The option `-cut` is used for breaking after first lexing leading to successful parse. The only nondeterministic lexer right now is `-lexer=subseqs`, which first filters with `-lexer=ignore` (dropping words neither in the grammar nor literals) and then starts ignoring other words from longest to shortest subsequence. This is usable for parser tasks of keyword spotting type, but expensive (2n) in long input. A smarter implementation is therefore desirable.

14/11 (AR) Functions can be made unparsable (or "internal" as in BNFC). This is done by `i -noparse=file`, where the nonparsable functions are given in `file` using the line format `--# noparse Funs`. This can be used e.g. to rule out expensive parsing rules. It is used in `lib/resource/abstract/LangVP.gf` to get parse values structured with `VP`, which is obtained via transfer. So far only the default (= old) parser generator supports this.

14/11 (AR) Removed the restrictions how a lincat may look like. Now any record type that has a value in GFC (i.e. without any functions in it) can be used, e.g. {np : NP ; cn : Bool => CN}. To display linearization values, only `l -record` shows nice results.

9/11 (AR) GF shell state can now have several abstract syntaxes with their associated concrete syntaxes. This allows e.g. parsing with resource while testing an application. One can also have a parse-transfer-lin chain from one abstract syntax to another.

7/11 (BB) Running commands can now be interrupted with Ctrl-C, without killing the GF process. This feature is not supported on Windows.

1/11 (AR) Yet another method for adding probabilities: append `--# prob Double` to the end of a line defining a function. This can be (1) a `.cf` rule (2) a `fun` rule, or (3) a `lin` rule. The probability is attached to the first identifier on the line.

1/11 (BB) Added generation of weighted SRGS grammars. The weights are calculated from the function probabilities. The algorithm for calculating the weights is not yet very good. Use `pg -printer=srgs_xml_prob`.

31/10 (BB) Added option for converting grammars to SRGS grammars in XML format. Use `pg -printer=srgs_xml`.

31/10 (AR) Probabilistic grammars. Probabilities can be used to weight random generation (`gr -prob`) and to rank parse results (`p -prob`). They are read from a separate file (flag `i -probs=File`, format `--# prob Fun Double`) or from the top-level grammar file itself (option `i -prob`). To see the probabilities, use `pg -printer=probs`.
As a by-product, the probabilistic random generation algorithm is available for any context-free abstract syntax. Use the flag `gr -cf`. This algorithm is much faster than the old (more general) one, but it may sometimes loop.

12/10 (AR) Flag `-atoms=Int` to the command `gt = generate_trees` takes away all zero-argument functions except Int per category. In this way, it is possible to generate a corpus illustrating each syntactic structure even when the lexicon (which consists of zero-argument functions) is large.

6/10 (AR) New commands `dc = define_command` and `dt = define_tree` to define macros in a GF session. See `help` for details and examples.

5/10 (AR) Printing missing linearization rules: `pm -printer=missing`. Command `g = grep`, which works in a way similar to Unix grep.

5/10 (PL) Printing graphs with function and category dependencies: `pg -printer=functiongraph`, `pg -printer=typegraph`.

20/9 (AR) Added optimization by common subexpression elimination. It works on GFC modules and creates `oper` definitions for subterms that occur more than once in `lin` definitions. These `oper` definitions are automatically reinlined in functionalities that don't support `oper`s in GFC. This conversion is done by module and the `oper`s are not inherited. Moreover, the subterms can contain free variables which means that the `oper`s are not always well typed. However, since all variables in GFC are type-specific (and local variables are `lin`-specific), this does not destroy subject reduction or cause illegal captures.
The optimization is triggered by the flag `optimize=OPT_subs`, where `OPT` is any of the other optimizations (see `h -optimize`). The most aggressive value of the flag is `all_subs`. In experiments, the size of a GFC module can shrink by 85% compared to plain `all`.

18/9 (AR) Removed superfluous spaces from GFC printing. This shrinks the GFC size by 5-10%.

15/9 (AR) Fixed some bugs in dependent-type type checking of abstract modules at compile time. The type checker is more severe now, which means that some old grammars may fail to compile - but this is usually the right result. However, the type checker of `def` judgements still needs work.

14/9 (AR) Added printing of grammars to a format without parameters, in the spirit of Peanos "Latino sine flexione". The command `pg -unpar` does the trick, and the result can be saved in a `gfcm` file. The generated concrete syntax modules get the prefix `UP_`. The translation is briefly:

      (P => T)*               =  T*
      (t ! p)*                =  t*
      (table {p => t ; ...})* =  t*

In order for this to be maximally useful, the grammar should be written in such a way that the first value of every parameter type is the desired one. For instance, in Peano's case it would be the ablative for noun cases, the singular for numbers, and the 2nd person singular imperative for verb forms.

14/9 (BB) Added finite state approximation of grammars. Internally the conversion is done `cfg -> regular -> fa -> slf`, so the different printers can be used to check the output of each stage. The new options are:

`pg -printer=slf`
  A finite automaton in the HTK SLF format.
`pg -printer=slf_graphviz`
  The same FA as in SLF, but in Graphviz format.
`pg -printer=fa_graphviz`
  A finite automaton with labelled edges, instead of labelled nodes which SLF has.
`pg -printer=regular`
  A regular grammar in a simple BNF.

4/9 (AR) Added the option `pg -printer=stat` to show statistics of gfc compilation result. To be extended with new information. The most important stats now are the top-40 sized definitions.

1/7 Release of GF 2.3.

1/7 (AR) Added the flag `-o` to the `vt` command to just write the `.dot` file without going to `.ps` (cf. 20/6).

29/6 (AR) The printer used by Embedded Java GF Interpreter (`pm -header`) now produces working code from all optimized grammars - hence you need not select a weaker optimization just to use the interpreter. However, the optimization `-optimize=share` usually produces smaller object grammars because the "unoptimizer" just undoes all optimizations. (This is to be considered a temporary solution until the interpreter knows how to handle stronger optimizations.)

27/6 (AR) The flag `flags optimize=noexpand` placed in a resource module prevents the optimization phase of the compiler when the `.gfr` file is created. This can prevent serious code explosion, but it will also make the processing of modules using the resource slowwer. A favourable example is `lib/resource/finnish/ParadigmsFin`.

23/6 (HD,AR) The new editor GUI `gfeditor` by Hans-Joachim Daniels can now be used. It is based on Janna Khegai's `jgf`. New functionality include HTML display (`gfeditor -h`) and programmable refinement tooltips.

23/6 (AR) The flag `unlexer=finnish` can be used to bind Finnish suffixes (e.g. possessives) to preceding words. The GF source notation is e.g. `"isä" ++ "&*" ++ "nsa" ++ "&*" ++ "ko"`, which unlexes to `"isänsäkö"`. There is no corresponding lexer support yet.

22/6 (PL,AR) The MCFG parser (`p -mcfg`) now works on all optimized grammars - hence you need not select a weaker optimization to use this parser. The same concerns the CFGM printer (`pm -printer=cfgm`).

20/6 (AR) Added the command `visualize_tree` = `vt`, to display syntax trees graphically. Like `vg`, this command uses GraphViz and Ghostview. The foremost use is to pipe the parser to this command.

17/6 (BB) There is now support for lists in GF abstract syntax. A list category is declared as:

    cat [C]

or

    cat [C]{n}

where `C` is a category and `n` is a non-negative integer. `cat [C]` is equivalent to `cat [C]{0}`. List category syntax can be used whereever categories are used.

`cat [C]{n}` is equivalent to the declarations:

    cat ListC
    fun BaseC : C^n -> ListC
    fun ConsC : C -> ListC -> ListC

where `C^0 -> X` means `X`, and `C^m` (where m > 0) means `C -> C^(m-1)`.

A lincat declaration on the form:

    lincat [C] = T

is equivalent to

    lincat ListC = T

The linearizations of the list constructors are written just like they would be if the function declarations above had been made manually, e.g.:

    lin BaseC x_1 ... x_n = t
    lin ConsC x xs = t'

10/6 (AR) Preprocessor of `.gfe` files can now be performed as part of any grammar compilation. The flag `-ex` causes GF to look for the `.gfe` files and preprocess those that are younger than the corresponding `.gf` files. The files are first sorted and grouped by the resource, so that each resource only need be compiled once.

10/6 (AR) Editor GUI can now be alternatively invoked by the shell command `gf -edit` (equivalent to `jgf`).

10/6 (AR) Editor GUI command `pc Int` to pop `Int` items from the clip board.

4/6 (AR) Sequence of commands in the Java editor GUI now possible. The commands are separated by `;;` (notice the space on both sides of the two semicolons). Such a sequence can be sent from the "GF Command" pop-up field, but is mostly intended for external processes that communicate with GF.

3/6 (AR) The format `.gfe` defined to support grammar writing by examples. Files of this format are first converted to `.gf` files by the command

      gf -examples File.gfe

See `../lib/resource/doc/examples/QuestionsI.gfe` for an example.

31/5 (AR) Default of p -rawtrees=k changed to 999999.

31/5 (AR) Support for restricted inheritance. Syntax:

      M          -- inherit everything from M, as before
      M [a,b,c]  -- only inherit constants a,b,c
      M-[a,b,c]  -- inherit everything except a,b,c

Caution: there is no check yet for completeness and consistency, but restricted inheritance can create run-time failures.

29/5 (AR) Parser support for reading GFC files line per line. The category `Line` in `GFC.cf` can be used as entrypoint instead of `Grammar` to achieve this.

28/5 (AR) Environment variables and path wild cards.

- `GF_LIB_PATH` gives the location of `GF/lib`
- `GF_GRAMMAR_PATH` gives a list of directories appended to the explicitly given path
- `DIR/*` is expanded to the union of all subdirectories of `DIR`

26/5/2005 (BB) Notation for list categories.