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-rw-r--r--prolog/util.py13
1 files changed, 11 insertions, 2 deletions
diff --git a/prolog/util.py b/prolog/util.py
index 83f891f..e1ce36b 100644
--- a/prolog/util.py
+++ b/prolog/util.py
@@ -196,8 +196,12 @@ def map_vars(a, b, tokens, variables):
# Return a set of predicate names (e.g. conc/3) used in [program].
def used_predicates(program):
predicates = set()
- def walk(tree):
+ def walk(tree, dcg=False):
if isinstance(tree, Tree):
+ # DCG predicates can be called without parameters
+ if tree.label() == 'clause' and len(tree) == 4 and \
+ tree[1].type == 'FROMDCG':
+ dcg = True
if tree.label() == 'term' and len(tree) >= 3 and \
isinstance(tree[0], Tree) and tree[0].label() == 'functor':
if len(tree) == 3:
@@ -205,7 +209,12 @@ def used_predicates(program):
else:
predicates.add('{}/{}'.format(tree[0][0], (len(tree[2])+1)//2))
for subtree in tree:
- walk(subtree)
+ walk(subtree, dcg)
+ elif isinstance(tree, Token):
+ if dcg and tree.type == 'NAME':
+ predicates.add('{}/{}'.format(tree.val, 2))
+ predicates.add('{}/{}'.format(tree.val, 3))
+ predicates.add('{}/{}'.format(tree.val, 4))
tree = parse(program)
if tree is not None:
walk(tree)