1 files changed, 149 insertions, 0 deletions
diff --git a/monkey/patterns.py b/monkey/patterns.py
new file mode 100644
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+++ b/monkey/patterns.py
@@ -0,0 +1,149 @@
+# CodeQ: an online programming tutor.
+# Copyright (C) 2016,2017 UL FRI
+#
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, either version 3 of the License, or (at your option) any
+# later version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+import collections
+from itertools import chain, combinations, product
+
+from nltk import Tree
+
+from prolog.util import parse as prolog_parse
+
+# construct pattern to match the structure of nodes given by [include],
+# supports variables and literals
+def pattern(node, include):
+    if not isinstance(node, Tree):
+        return None
+
+    label = node.label()
+    if any(n is node for n in include):
+        if label == 'literal':
+            return '"{}"'.format(node[0].val)
+        if label == 'variable':
+            return '{}'.format(label)
+        return None
+    if label == 'functor':
+        return '({} "{}")'.format(label, node[0].val)
+
+    subpats = [pattern(child, include) for child in node]
+    pat = None
+    if any(subpats):
+        if label == 'and':
+            if subpats[1]:
+                pat = subpats[1]
+            if subpats[0]:
+                if pat:
+                    pat = subpats[0] + ' ' + pat
+                else:
+                    pat = subpats[0]
+        elif label == 'args':
+            pat = label
+            for i, subpat in enumerate(subpats):
+                if subpat:
+                    pat += ' {}'.format(subpat)
+            pat = '(' + pat + ')'
+        elif label == 'unop':
+            pat = '(' + label + ' ' + node[0].val + ' ' + subpats[1] + ')'
+        elif label == 'binop':
+            pat = label
+            if subpats[0]:
+                pat += ' {}'.format(subpats[0])
+            pat += ' "{}"'.format(node[1].val)
+            if subpats[2]:
+                pat += ' {}'.format(subpats[2])
+            pat = '(' + pat + ')'
+        elif label == 'clause':
+            pat = label
+            for i, subpat in enumerate(subpats):
+                if subpat:
+                    pat += ' {}'.format(subpats[i])
+            return '(' + pat + ')'
+        elif label == 'compound':
+            if len(subpats) > 1 and subpats[1]:
+                pat = label
+                for i, subpat in enumerate(subpats):
+                    pat += ' {}'.format(subpat)
+                pat = '(' + pat + ')'
+            else:
+                return None
+        elif label == 'head':
+            pat = label
+            pat += ' {}'.format(subpats[0])
+            pat = '(' + pat + ')'
+        elif label == 'list':
+            pat = 'list '
+            if subpats[0]:
+                pat += '(h {})'.format(subpats[0])
+            if subpats[0] and subpats[1]:
+                pat += ' '
+            if subpats[1]:
+                pat += '(t {})'.format(subpats[1])
+            pat = '(' + pat + ')'
+        if not pat:
+            for s in subpats:
+                if s:
+                    pat = s
+                    break
+    return pat
+
+def get_patterns(tree):
+    if isinstance(tree, str):
+        tree = prolog_parse(tree)
+        if tree is None:
+            return
+
+    # get patterns separately for each clause
+    for clause in tree:
+        # collect variable nodes in this clause
+        variables = collections.defaultdict(list)
+        for node in clause.subtrees():
+            if isinstance(node, Tree) and node.label() == 'variable':
+                name = node[0].val
+                variables[name].append(node)
+
+        # yield patterns for singleton variables
+        for var, nodes in variables.items():
+            if len(nodes) == 1:
+                pat = pattern(clause, nodes)
+                if pat:
+                    yield pat, nodes
+
+        # yield patterns for variable-variable pairs (within a clause)
+        for var, nodes in variables.items():
+            for selected in combinations(nodes, 2):
+                pat = pattern(clause, selected)
+                if pat:
+                    yield pat, selected
+
+        # yield patterns for variable-literal / literal-literal pairs
+        # yield patterns for singleton literals
+        # (only within a topmost compound / binop / unop)
+        def patterns_with_literals(node):
+            if not isinstance(node, Tree):
+                return
+            if node.label() in {'compound', 'binop', 'unop'}:
+                vars = [n for n in node.subtrees() if n.label() == 'variable']
+                lits = [n for n in node.subtrees() if n.label() == 'literal']
+                for selected in chain(
+                        combinations(lits, 1),
+                        combinations(lits, 2),
+                        product(lits, vars)):
+                    pat = pattern(clause, selected)
+                    if pat:
+                        yield pat, selected
+            else:
+                for child in node:
+                    yield from patterns_with_literals(child)
+        yield from patterns_with_literals(clause)