S ::= NP VP ; VP ::= V | TV NP | "is" A ; @@ -93,12 +93,12 @@ understand. Type (or copy) the following lines in a file named -Importing grammars and parsing strings
+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.- import stoneage.gf + import paleolithic.gfThe GF program now compiles your grammar into an internal representation, and shows a new prompt when it is ready. @@ -131,7 +131,7 @@ you imported. Try parsing something else, and you fail -Generating trees and strings
+Generating trees and strings
You can also use GF for linearizing (linearize = l). This is the inverse of @@ -158,7 +158,7 @@ a pipe. -Some random-generated sentences
+Some random-generated sentences
Random generation can be quite amusing. So you may want to generate ten strings with one and the same command: @@ -178,7 +178,7 @@ generate ten strings with one and the same command: -Systematic generation
+Systematic generation
To generate all sentence that a grammar can generate, use the command generate_trees = gt. @@ -203,7 +203,7 @@ trees in your grammar, it would never terminate. Why? -More on pipes; tracing
+More on pipes; tracing
A pipe of GF commands can have any length, but the "output type" (either string or tree) of one command must always match the "input type" @@ -227,7 +227,7 @@ contains strings that can be parsed in more than one way. -Writing and reading files
+Writing and reading files
To save the outputs of GF commands into a file, you can pipe it to the write_file = wf command, @@ -248,9 +248,7 @@ a sentence but a sequence of ten sentences. -Labelled context-free grammars
- -Rules and labels
+Labelled context-free grammars
The syntax trees returned by GF's parser in the previous examples are not so nice to look at. The identifiers of form Mks @@ -280,7 +278,313 @@ is the label of the rule prefixing this to a common noun, Mks_18 is the label of the adjective thick, and so on. + +The labelled context-free format
+The labelled context-free grammar format permits user-defined +labels to each rule. GF recognizes files of this format by the suffix +.cf. Let us include the following rules in the file +paleolithic.cf. ++ PredVP. S ::= NP VP ; + UseV. VP ::= V ; + ComplTV. VP ::= TV NP ; + UseA. VP ::= "is" A ; + This. NP ::= "this" CN ; + That. NP ::= "that" CN ; + Def. NP ::= "the" CN ; + Indef. NP ::= "a" CN ; + ModA. CN ::= A CN ; + Bird. CN ::= "bird" ; + Boy. CN ::= "boy" ; + Man. CN ::= "man" ; + Louse. CN ::= "louse" ; + Snake. CN ::= "snake" ; + Worm. CN ::= "worm" ; + Big. A ::= "big" ; + Green. A ::= "green" ; + Rotten. A ::= "rotten" ; + Thick. A ::= "thick" ; + Warm. A ::= "warm" ; + Laugh. V ::= "laughs" ; + Sleep. V ::= "sleeps" ; + Swim. V ::= "swims" ; + Eat. TV ::= "eats" ; + Kill. TV ::= "kills" + Wash. TV ::= "washes" ; ++ + +Using the labelled context-free format
+ +The GF commands for the .cf format are +exactly the same as for the .ebnf format. +Just the syntax trees become nicer to read and +to remember. Notice that before reading in +a new grammar in GF you often (but not always, +as we will see later) have first to give the +command (empty = e), which removes the +old grammar from the GF shell state. ++ > empty + + > i paleolithic.cf + + > p "the boy eats a snake" + PredVP (Def Boy) (ComplTV Eat (Indef Snake)) + + > gr -tr | l + PredVP (Indef Louse) (UseA Big) + a louse is big ++ + + +The GF grammar format
+ +To see what there really is in GF's shell state when a grammar +has been imported, you can give the plain command +print_grammar = pg. ++ > print_grammar ++The output is quite unreadable at this stage, and you may feel happy that +you did not need to write the grammar in that notation, but that the +GF grammar compiler produced it. + ++ +However, we will now start to show how GF's own notation gives you +much more expressive power than the .cf and .ebnf +formats. We will introduce the .gf format by presenting +one more way of defining the same grammar as in +paleolithic.cf and paleolithic.ebnf. +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: +
+ PredVP. S ::= NP VP ; ++is interpreted as the following pair of rules: +
+ fun PredVP : NP -> VP -> S ;
+ lin PredVP x y = {s = x.s ++ y.s} ;
+
+The former rule, with the keyword fun, belongs to the abstract syntax.
+It defines the function
+PredVP which constructs syntax trees of form
+(PredVP x y).
+
++ +The latter rule, with the keyword lin, belongs to the concrete syntax. +It defines the linearization function for +syntax trees of form (PredVP x y). + + + +
+abstract Paleolithic = {
+cat
+ S ; NP ; VP ; CN ; A ; V ; TV ;
+fun
+ PredVP : NP -> VP -> S ;
+ UseV : V -> VP ;
+ ComplTV : TV -> NP -> VP ;
+ UseA : A -> VP ;
+ ModA : A -> CN -> CN ;
+ This, That, Def, Indef : CN -> NP ;
+ Bird, Boy, Man, Louse, Snake, Worm : CN ;
+ Big, Green, Rotten, Thick, Warm : A ;
+ Laugh, Sleep, Swim : V ;
+ Eat, Kill, Wash : TV ;
+}
+
+Notice the use of shorthands permitting the sharing of
+the keyword in subsequent judgements, and of the type
+in subsequent fun judgements.
+
+
+
+
+concrete PaleolithicEng of Paleolithic = {
+lincat
+ S, NP, VP, CN, A, V, TV = {s : Str} ;
+lin
+ PredVP np vp = {s = np.s ++ vp.s} ;
+ UseV v = v ;
+ ComplTV tv np = {s = tv.s ++ np.s} ;
+ UseA a = {s = "is" ++ a.s} ;
+ This cn = {s = "this" ++ cn.s} ;
+ That cn = {s = "that" ++ cn.s} ;
+ Def cn = {s = "the" ++ cn.s} ;
+ Indef cn = {s = "a" ++ cn.s} ;
+ ModA a cn = {s = a.s ++ cn.s} ;
+ Bird = {s = "bird"} ;
+ Boy = {s = "boy"} ;
+ Louse = {s = "louse"} ;
+ Man = {s = "man"} ;
+ Snake = {s = "snake"} ;
+ Worm = {s = "worm"} ;
+ Big = {s = "big"} ;
+ Green = {s = "green"} ;
+ Rotten = {s = "rotten"} ;
+ Thick = {s = "thick"} ;
+ Warm = {s = "warm"} ;
+ Laugh = {s = "laughs"} ;
+ Sleep = {s = "sleeps"} ;
+ Swim = {s = "swims"} ;
+ Eat = {s = "eats"} ;
+ Kill = {s = "kills"} ;
+ Wash = {s = "washes"} ;
+}
+
+
+
+
++ +Each module is compiled into a .gfc file. + +
+ +Import PaleolithicEng.gf and try what happens +
+ ++Nothing more than before, except that the GFC files +are generated. + + + +
+concrete PaleolithicIta of Paleolithic = {
+lincat
+ S, NP, VP, CN, A, V, TV = {s : Str} ;
+lin
+ PredVP np vp = {s = np.s ++ vp.s} ;
+ UseV v = v ;
+ ComplTV tv np = {s = tv.s ++ np.s} ;
+ UseA a = {s = "è" ++ a.s} ;
+ This cn = {s = "questo" ++ cn.s} ;
+ That cn = {s = "quello" ++ cn.s} ;
+ Def cn = {s = "il" ++ cn.s} ;
+ Indef cn = {s = "un" ++ cn.s} ;
+ ModA a cn = {s = cn.s ++ a.s} ;
+ Bird = {s = "uccello"} ;
+ Boy = {s = "ragazzo"} ;
+ Louse = {s = "pidocchio"} ;
+ Man = {s = "uomo"} ;
+ Snake = {s = "serpente"} ;
+ Worm = {s = "verme"} ;
+ Big = {s = "grande"} ;
+ Green = {s = "verde"} ;
+ Rotten = {s = "marcio"} ;
+ Thick = {s = "grosso"} ;
+ Warm = {s = "caldo"} ;
+ Laugh = {s = "ride"} ;
+ Sleep = {s = "dorme"} ;
+ Swim = {s = "nuota"} ;
+ Eat = {s = "mangia"} ;
+ Kill = {s = "uccide"} ;
+ Wash = {s = "lava"} ;
+}
+
+
+
++ ++Try generation now: +
+ ++Translate by using a pipe: +
+ ++Inspect the shell state (print_options = po): +
+ > print_options + main abstract : Paleolithic + main concrete : PaleolithicIta + all concretes : PaleolithicIta PaleolithicEng ++ + + +