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

Stabler - Lx 185/209 2003
feature(Attribute, Node, Value) :- features(Node, Features), member(Attribute:Value, Features).
(12) Let’s say that a terminal node is a leaf with phonetic content, and an empty node is a leaf with no
phonetic content:
terminal(n(_,_/ -Word,_), Word).
empty(n(_,_/[],_)).
nonempty(Node) :- terminal(Node).
nonempty(Node) :- children(Node,[_|_]).
(13) To extend a set of features at a node, it is convenient to have:
add_feature(Node0, Attribute, Value, Node) :category(Node0,
Category), category(Node, Category),
barlevel(Node0, Barlevel), barlevel(Node, Barlevel),
extended(Node0, EP), extended(Node, EP),
features(Node0, Features0), features(Node, Features),
( member(Attribute:Value0, Features0)
-> Value = Value0, Features = Features0
; Features = [Attribute:Value|Features0]
).
And to copy the values of a list of attributes:
copy_features([], OldFeatures, []).
copy_features([Att|Atts], OldFeatures, Features0) :-
( member(Att:Val, OldFeatures)
-> Features0 = [Att:Val|Features]
; Features0 = Features
),
copy_features(Atts, OldFeatures, Features).
65