paleolithic.ebnf:
+paleolithic.cf:
S ::= NP VP ;
@@ -120,38 +133,48 @@ understand. Type (or copy) the following lines in a file named
stoneage,
which implements a fragment of primitive language. This fragment
was defined by the linguist Morris Swadesh as a tool for studying
-the historical relations of languages. But as pointed out
+the historical relations of languages. But as suggested
in the Wiktionary article on
Swadesh list, the
-fragment is also usable for basic communication with foreigners.)
+fragment is also usable for basic communication between foreigners.)
Importing grammars and parsing strings
The first GF command when using a grammar is to import it.
The command has a long name, import, and a short name, i.
+You can type either
- import paleolithic.gf
+ import paleolithic.cf
+
-The GF program now compiles your grammar into an internal
+or
+
+
+ i paleolithic.cf
+
+
+
+to get the same effect.
+The effect is that the GF program compiles your grammar into an internal
representation, and shows a new prompt when it is ready.
-You can use GF for parsing:
+You can now use GF for parsing:
> parse "the boy eats a snake"
- Mks_0 (Mks_6 Mks_9) (Mks_2 Mks_20 (Mks_7 Mks_11))
+ S_NP_VP (NP_the_CN CN_boy) (VP_TV_NP TV_eats (NP_a_CN CN_snake))
> parse "the snake eats a boy"
- Mks_0 (Mks_6 Mks_11) (Mks_2 Mks_20 (Mks_7 Mks_9))
+ S_NP_VP (NP_the_CN CN_snake) (VP_TV_NP TV_eats (NP_a_CN CN_boy))
The parse (= p) command takes a string
(in double quotes) and returns an abstract syntax tree - the thing
-with Mkss and parentheses. We will see soon how to make sense
+beginning with S_NP_VP. We will see soon how to make sense
of the abstract syntax trees - now you should just notice that the tree
is different for the two strings.
@@ -161,7 +184,7 @@ you imported. Try parsing something else, and you fail
> p "hello world"
- No success in cf parsing
+ No success in cf parsing hello world
no tree found
@@ -173,8 +196,8 @@ You can also use GF for linearizing
parsing, taking trees into strings:
- > linearize Mks_0 (Mks_6 Mks_11) (Mks_2 Mks_20 (Mks_7 Mks_9))
- the snake eats a boy
+ > linearize S_NP_VP (NP_the_CN CN_boy) (VP_TV_NP TV_eats (NP_a_CN CN_snake))
+ the boy eats a snake
What is the use of this? Typically not that you type in a tree at
@@ -184,7 +207,7 @@ you can obtain a tree from somewhere else. One way to do so is
> generate_random
- Mks_0 (Mks_4 Mks_11) (Mks_3 Mks_15)
+ S_NP_VP (NP_this_CN (CN_A_CN A_thick CN_worm)) (VP_V V_sleeps)
Now you can copy the tree and paste it to the linearize command.
@@ -197,6 +220,24 @@ a pipe.
+Visualizing trees
+
+The gibberish code with parentheses returned by the parser does not
+look like trees. Why is it called so? Trees are a data structure that
+represent <b>nesting</b>: trees are branching entities, and the branches
+are themselves trees. Parentheses give a linear representation of trees,
+useful for the computer. But the human eye may prefer to see a visualization;
+for this purpose, GF provides the command visualizre_tree = vt, to which
+parsing (and any other tree-producing command) can be piped:
+
+ parse "the green boy eats a warm snake" | vt ++ +
+
+
Some random-generated sentences
Random generation can be quite amusing. So you may want to @@ -216,7 +257,7 @@ generate ten strings with one and the same command: a boy is green
- +Systematic generation
To generate <i>all<i> sentence that a grammar
@@ -246,7 +287,7 @@ You get quite a few trees but not all of them: only up to a given
Quiz. If the command gt generated all
trees in your grammar, it would never terminate. Why?
More on pipes; tracing
A pipe of GF commands can have any length, but the "output type" @@ -269,7 +310,7 @@ This facility is good for test purposes: for instance, you may want to see if a grammar is ambiguous, i.e. contains strings that can be parsed in more than one way.
- +Writing and reading files
To save the outputs of GF commands into a file, you can @@ -292,7 +333,7 @@ the file separately. Without the flag, the grammar could not recognize the string in the file, because it is not a sentence but a sequence of ten sentences.
- +Labelled context-free grammars
The syntax trees returned by GF's parser in the previous examples @@ -389,7 +430,7 @@ old grammar from the GF shell state. a louse is thick
- +The GF grammar format
To see what there really is in GF's shell state when a grammar @@ -413,7 +454,7 @@ one more way of defining the same grammar as in Then we will show how the full GF grammar format enables you to do things that are not possible in the weaker formats.
- +Abstract and concrete syntax
A GF grammar consists of two main parts: @@ -893,7 +934,7 @@ The graph uses
<img src="Gatherer.gif">
- +Resource modules
Suppose we want to say, with the vocabulary included in @@ -1039,7 +1080,7 @@ Resource modules can extend other resource modules, in the same way as modules of other types can extend modules of the same type.
- +Opening a ``resource``
Any number of resource modules can be
@@ -1386,36 +1427,29 @@ GF currently requires that all fields in linearization records that
have a table with value type Str have as labels
either s or s with an integer index.
Topics still to be written
--Free variation -
--Record extension, tuples -
--Predefined types and operations -
--Lexers and unlexers -
--Grammars of formal languages -
--Resource grammars and their reuse -
--Embedded grammars in Haskell and Java -
--Dependent types, variable bindings, semantic definitions -
--Transfer rules -
+ +