Notes on computational linguistics.pdf - UCLA Department of ...

Stabler - Lx 185/209 2003
(27) With this definition, if we also load the following theory,
p :˜ [q,r].
q :˜ [].
r :˜ [].
then we get the following session:
| ?- [] ?˜ [p]@[T].
T = p/[q/[], r/[]] ;
No
| ?- [] ?˜ [p,q]@[T0,T].
T0 = p/[q/[], r/[]]
T = q/[] ;
No
What we are more interested in is proofs from grammars, so here is a session showing the use of our
simple grammar g1.pl from page 45:
| ?- [tdp,g1].
Yes
| ?- [the,idea,will,suffice] ?˜ [ip]@[T].
T = ip/[dp/[d1/[d0/[the/[]], np/[n1/[n0/[idea/[]]]]]], i1/[i0/[will/[]], vp/[v1/[v0/[suffice/[]]]]]]
3.6 Some basic relations on trees
3.6.1 “Pretty printing” trees
(28) Those big trees are not so easy to read! It is common to use a “pretty printer” to produce a more readable
text display. Here is the simple pretty printer:
/*
* file: pp_tree.pl
*/
pp_tree(T) :- pp_tree(T, 0).
pp_tree(Cat/Ts, Column) :- !, tab(Column), write(Cat), write(’ /[’), pp_trees(Ts, Column).
pp_tree(X, Column) :- tab(Column), write(X).
pp_trees([], _) :- write(’]’).
pp_trees([T|Ts], Column) :- NextColumn is Column+4, nl, pp_tree(T, NextColumn), pp_rest_trees(Ts, NextColumn).
pp_rest_trees([], _) :- write(’]’).
pp_rest_trees([T|Ts], Column) :- write(’,’), nl, pp_tree(T, Column), pp_rest_trees(Ts, Column).
The only reason to study the implementation of this pretty printer is as an optional exercise prolog.
What is important is that we be able to use it for the work we do that is more directly linguistic.
(29) Here is how to use the pretty printer:
| ?- [tdp,g1,pp_tree].
Yes
| ?- ([the,idea,will,suffice] ?˜ [ip]@[T]),pp_tree(T).
ip /[
dp /[
d1 /[
d0 /[
the /[]],
np /[
n1 /[
n0 /[
idea /[]]]]]],
i1 /[
i0 /[
will /[]],
vp /[
v1 /[
v0 /[
suffice /[]]]]]]
T = ip/[dp/[d1/[d0/[the/[]],np/[n1/[...]]]],i1/[i0/[will/[]],vp/[v1/[v0/[...]]]]] ?
Yes
48