Add convenience methods for deriv (pre)terminals

Fixes #105

CHANGELOG.md

@@ -7,6 +7,8 @@
 * `delphin.itsdb.ItsdbProfile.exists()` (#112)
 * `delphin.itsdb.ItsdbProfile.size()` (#112)
 * `--in-place` option to the `delphin mkprof` command (#109)
+* `delphin.derivation.UdfNode.preterminals()` (#105)
+* `delphin.derivation.UdfNode.terminals()` (#105)
 
 ### Changed
 

delphin/derivation.py

@@ -374,6 +374,32 @@ def lexical_type(self):
         warnings.warn('Deprecated; try UdfNode.type', DeprecationWarning)
         return self.type
 
+    # Convenience methods
+
+    def preterminals(self):
+        """
+        Return the list of preterminals (i.e. lexical grammar-entities).
+        """
+        nodes = []
+        for dtr in self.daughters:
+            if isinstance(dtr, UdfTerminal):
+                nodes.append(self)
+            else:
+                nodes.extend(dtr.preterminals())
+        return nodes
+
+    def terminals(self):
+        """
+        Return the list of terminals (i.e. lexical units).
+        """
+        nodes = []
+        for dtr in self.daughters:
+            if isinstance(dtr, UdfTerminal):
+                nodes.append(dtr)
+            else:
+                nodes.extend(dtr.terminals())
+        return nodes
+
 class Derivation(UdfNode):
     """
     A class for reading, writing, and storing derivation trees. Objects

tests/derivation_test.py

@@ -323,6 +323,38 @@ def test_lexical_type(self):
             assert node.daughters[0].lexical_type() == 'a-type_le'
             assert node.daughters[1].lexical_type() == 'b-type_le'
 
+    def test_preterminals(self):
+        a = D.from_string('(root (1 some-thing -1 -1 -1'
+                          '  (2 a-thing -1 -1 -1 ("a"))'
+                          '  (3 b-thing -1 -1 -1 ("b"))))')
+        assert [t.id for t in a.preterminals()] == [2, 3]
+        a = D.from_string('(root'
+            ' (1 some-thing@some-type 0.4 0 5'
+            '  (2 a-lex@a-type 0.8 0 1'
+            '   ("a b"'
+            '    3 "token [ +FORM \\"a\\" ]"'
+            '    4 "token [ +FORM \\"b\\" ]"))'
+            '  (5 b-lex@b-type 0.9 1 2'
+            '   ("b"'
+            '    6 "token [ +FORM \\"b\\" ]"))))')
+        assert [t.id for t in a.preterminals()] == [2, 5]
+
+    def test_terminals(self):
+        a = D.from_string('(root (1 some-thing -1 -1 -1'
+                          '  (2 a-thing -1 -1 -1 ("a"))'
+                          '  (3 b-thing -1 -1 -1 ("b"))))')
+        assert [t.form for t in a.terminals()] == ['a', 'b']
+        a = D.from_string('(root'
+            ' (1 some-thing@some-type 0.4 0 5'
+            '  (2 a-lex@a-type 0.8 0 1'
+            '   ("a b"'
+            '    3 "token [ +FORM \\"a\\" ]"'
+            '    4 "token [ +FORM \\"b\\" ]"))'
+            '  (5 b-lex@b-type 0.9 1 2'
+            '   ("b"'
+            '    6 "token [ +FORM \\"b\\" ]"))))')
+        assert [t.form for t in a.terminals()] == ['a b', 'b']
+
     def test_to_udf(self):
         s = '(1 some-thing -1 -1 -1 ("token"))'
         assert D.from_string(s).to_udf(indent=None) == s