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version 3 of quick reference

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aarne
2006-04-04 07:41:32 +00:00
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doc/gf-reference.txt
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@@ -9,19 +9,23 @@ Aarne Ranta
%!target:html
This is a quick reference on GF grammars.
This is a quick reference on GF grammars. It aims to
cover all forms of expression available when writing
grammars. It assumes basic knowledge of GF, which
can be acquired from the
[GF Tutorial http://www.cs.chalmers.se/~aarne/GF/doc/tutorial/].
Help on GF commands is obtained on line by the
help command (``h``).
help command (``help``), and help on invoking
GF with (``gf -help``).
==A Quick Example==
===A complete example===
This is a complete example, dividing a grammar
into three files.
This is a complete example of a GF grammar divided
into three modules in files. The grammar recognizes the
phrases //one pizza// and //two pizzas//.
``abstract``, ``concrete``, and ``resource``.
File ``Order.gf``
File ``Order.gf``:
```
abstract Order = {
cat
@@ -54,7 +58,7 @@ param Num = Sg | Pl ;
oper regNoun : Str -> {s : Num => Str} =
\dog -> {s = table {
Sg => dog ;
Pl => dog + "s"
_ => dog + "s"
}
} ;
}
@@ -69,7 +73,7 @@ To use this example, do
==Modules and files==
===Modules and files===
One module per file.
File named ``Foo.gf`` contains module named
@@ -122,7 +126,7 @@ Comments have the forms
```
-- till the end of line
{- any number of lines between -}
--# reserved for compiler pragmas
--# used for compiler pragmas
```
A ``concrete`` can be opened like a ``resource``.
It is translated as follows:
@@ -138,7 +142,7 @@ Any ``concrete`` of it then works as an ``instance``.
==Judgements==
===Judgements===
```
cat C -- declare category C
@@ -179,7 +183,7 @@ fun f,g : A -- same as fun f : A ; g : A
```
==Types==
===Types===
Abstract syntax (in ``fun``):
```
@@ -208,7 +212,7 @@ Ints n -- type of n first integers
```
Resource (in ``oper``): all those of concrete, plus
```
Tok -- tokens (subset of Str)
Tok -- tokens (subtype of Str)
A -> B -- functions from A to B
Int -- integers
Strs -- list of prefixes (for pre)
@@ -216,12 +220,12 @@ PType -- parameter type
Type -- any type
```
As parameter types, one can use any finite type:
``param`` constants ``P``,
``P`` defined in ``param P``,
``Ints n``, and record types of parameter types.
==Expressions==
===Expressions===
Syntax trees = full function applications
```
@@ -232,7 +236,7 @@ f a b -- : C if fun f : A -> B -> C
```
Higher-Order Abstract syntax (HOAS): functions as arguments:
```
F a (\y -> b) -- : C if a : A, b : B (x : A),
F a (\x -> c) -- : C if a : A, c : C (x : B),
fun F : A -> (B -> C) -> C
```
Tokens and token lists
@@ -260,7 +264,7 @@ table { -- by pattern matching
_ => "mouse" -- wildcard pattern
}
table {
n => regn n "cat" ;-- variable pattern
n => regn n "cat" -- variable pattern
}
table Num {...} -- table given with arg. type
table ["ox"; "oxen"] -- table as course of values
@@ -274,7 +278,6 @@ Records
```
{s = "Liz"; g = Fem} -- record in full form
{s,t = "et"} -- same as {s = "et";t= "et"}
{s = "Liz"} ** -- record extension: same as
{g = Fem} {s = "Liz" ; g = Fem}
@@ -318,13 +321,14 @@ lin F A B = {s = ["for all"] ++ A.s ++ B.$1 ++ B.s}
```
==Pattern matching==
===Pattern matching===
These patterns can be used in branches of ``table`` and
``case`` expressions.
``case`` expressions. Patterns are matched in the order in
which they appear in the grammar.
```
C -- atomic param constructor
C p q -- param constr. appl- to patterns
C p q -- param constr. applied to patterns
x -- variable, matches anything
_ -- wildcard, matches anything
"foo" -- string
@@ -338,7 +342,7 @@ p + "s" -- sequence of two string patterns
p* -- repetition of a string pattern
```
==Sample library functions==
===Sample library functions===
```
-- lib/prelude/Predef.gf
@@ -371,7 +375,7 @@ oper
```
==Flags==
===Flags===
Flags can appear, with growing priority,
- in files, judgement ``flags`` and without dash (``-``)
@@ -400,14 +404,14 @@ optimize=values good for lexicon concrete
optimize=all usually good for resource
optimize=noexpand for resource, if =all too big
```
For the full set of values for ``flag``,
use on-line ``h -flag``.
For the full set of values for ``FLAG``,
use on-line ``h -FLAG``.
==File paths==
===File paths===
Colon-separated lists of directories tried in the
Colon-separated lists of directories searched in the
given order:
```
--# -path=.:../abstract:../common:prelude
@@ -417,12 +421,12 @@ first line in the top file, as flag to ``gf``
when invoked, or as flag to the ``i`` command.
The prefix ``--#`` is used only in files.
If the variabls ``GF_LIB_PATH`` is defined, its
If the environment variabls ``GF_LIB_PATH`` is defined, its
value is automatically prefixed to each directory to
extend the original search path.
==Alternative grammar formats==
===Alternative grammar formats===
**Old GF** (before GF 2.0):
all judgements in any kinds of modules,
@@ -442,7 +446,7 @@ Rules must be one per line. The RHS can be empty.
S ::= (NP+ ("is" | "was") AP | V NP*) ;
```
where the RHS is a regular expression of categories
and quoted tokens: ``"foo", T U, T|U, T*, T+, T?``, or empty.
and quoted tokens: ``"foo", CAT, T U, T|U, T*, T+, T?``, or empty.
Rule labels are generated automatically.
@@ -465,7 +469,7 @@ are preprocessed by using a parser given by the flag
and the result is written to ``foo.gf``.
==References==
===References===
[GF Homepage http://www.cs.chalmers.se/~aarne/GF/]