Script started on XXX XXX XX 11:54:43 XXXX
 > cat g2.p

       snt --> det(F, Number), adjs(F), noun(Number), verb(Number).
       det(F, sing) --> [a], { F = consonant } ;
                        [an], { F = vowel }.
       det(_, plur) --> [the].
       adjs(F) --> adj(F); adj(F), adjs(_).
       adj(F) --> [spotted], { F = consonant } ;
                  [endangered], { F = vowel } ;
                  [poison_arrow], { F = consonant }.
       noun(Num) --> [frog], { Num = sing } ;
                     [owl], { Num = sing } ;
                     [frogs], { Num = plur } ;
                     [owls], { Num = plur }.

       verb(Num) --> [hops], { Num = sing } ;
                     [hop], { Num = plur } ;
                     [swims], { Num = sing } ;
                     [swim], { Num = plur } ;
                     [hunts], { Num = sing } ;
                     [hunt], { Num = plur } ;
                     [flies], { Num = sing } ;
                     [fly], { Num = plur }.

 > pl

Welcome to SWI-Prolog (Multi-threaded, Version 5.6.24)
Copyright (c) 1990-2006 University of Amsterdam.
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.

For help, use ?- help(Topic). or ?- apropos(Word).

?- ['g2.p'].
% g2.p compiled 0.00 sec, 5,624 bytes

Yes
?- snt(X,[]).

X = [a, spotted, frog, hops] ;

X = [a, spotted, frog, swims] ;

X = [a, spotted, frog, hunts] ;

X = [a, spotted, frog, flies] ;

X = [a, spotted, owl, hops] ;

X = [a, spotted, owl, swims] ;

X = [a, spotted, owl, hunts] ;

X = [a, spotted, owl, flies] ;

X = [a, poison_arrow, frog, hops] ;

X = [a, poison_arrow, frog, swims] ;

X = [a, poison_arrow, frog, hunts] 

Yes

?- Det = the, snt([Det | Rest], []), X = [Det | Rest].

Det = the
Rest = [spotted, frogs, hop]
X = [the, spotted, frogs, hop] ;

Det = the
Rest = [spotted, frogs, swim]
X = [the, spotted, frogs, swim] ;

Det = the
Rest = [spotted, frogs, hunt]
X = [the, spotted, frogs, hunt] ;

Det = the
Rest = [spotted, frogs, fly]
X = [the, spotted, frogs, fly] ;

Det = the
Rest = [spotted, owls, hop]
X = [the, spotted, owls, hop] ;

Det = the
Rest = [spotted, owls, swim]
X = [the, spotted, owls, swim] ;

Det = the
Rest = [spotted, owls, hunt]
X = [the, spotted, owls, hunt] ;

Det = the
Rest = [spotted, owls, fly]
X = [the, spotted, owls, fly] ;

Det = the
Rest = [endangered, frogs, hop]
X = [the, endangered, frogs, hop] ;

Det = the
Rest = [endangered, frogs, swim]
X = [the, endangered, frogs, swim] ;

Det = the
Rest = [endangered, frogs, hunt]
X = [the, endangered, frogs, hunt] ;

Det = the
Rest = [endangered, frogs, fly]
X = [the, endangered, frogs, fly] ;

Det = the
Rest = [endangered, owls, hop]
X = [the, endangered, owls, hop] ;

Det = the
Rest = [endangered, owls, swim]
X = [the, endangered, owls, swim] ;

Det = the
Rest = [endangered, owls, hunt]
X = [the, endangered, owls, hunt] ;

Det = the
Rest = [endangered, owls, fly]
X = [the, endangered, owls, fly] ;

Det = the
Rest = [poison_arrow, frogs, hop]
X = [the, poison_arrow, frogs, hop] ;

Det = the
Rest = [poison_arrow, frogs, swim]
X = [the, poison_arrow, frogs, swim] ;

Det = the
Rest = [poison_arrow, frogs, hunt]
X = [the, poison_arrow, frogs, hunt] ;

Det = the
Rest = [poison_arrow, frogs, fly]
X = [the, poison_arrow, frogs, fly] ;

Det = the
Rest = [poison_arrow, owls, hop]
X = [the, poison_arrow, owls, hop] ;

Det = the
Rest = [poison_arrow, owls, swim]
X = [the, poison_arrow, owls, swim] ;

Det = the
Rest = [poison_arrow, owls, hunt]
X = [the, poison_arrow, owls, hunt] ;

Det = the
Rest = [poison_arrow, owls, fly]
X = [the, poison_arrow, owls, fly] ;

Det = the
Rest = [spotted, spotted, frogs, hop]
X = [the, spotted, spotted, frogs, hop] 

Yes
?- halt.

 > exit
 >
script done on XXX XXX XX 12:03:11 XXXX