Fix ops; Add new tests that check transform using ops

Author: Krzysztof Czajkowski

editdistance/_edit_distance_osa.cpp

@@ -77,15 +77,15 @@ std::vector<std::vector<CppEditop>> backtrack_all_paths(
     const double tol = 1e-6;
 
     if (i > 0 && std::abs((dp[i-1][j] + delete_weight) - current_cost) < tol) {
-        CppEditop op(DELETE, i-1, i-1, delete_weight, std::string(1, a[i-1]));
+        CppEditop op(DELETE, i-1, j, delete_weight, std::string(1, a[i-1]));
         current_path.push_back(op);
         auto paths = backtrack_all_paths(a, b, dp, i-1, j, current_path, replace_weight, insert_weight, delete_weight, swap_weight);
         all_paths.insert(all_paths.end(), paths.begin(), paths.end());
         current_path.pop_back();
     }
 
     if (j > 0 && std::abs((dp[i][j-1] + insert_weight) - current_cost) < tol) {
-        CppEditop op(INSERT, i, i, insert_weight, std::string(1, b[j-1]));
+        CppEditop op(INSERT, i, j-1, insert_weight, std::string(1, b[j-1]));
         current_path.push_back(op);
         auto paths = backtrack_all_paths(a, b, dp, i, j-1, current_path, replace_weight, insert_weight, delete_weight, swap_weight);
         all_paths.insert(all_paths.end(), paths.begin(), paths.end());

editdistance/edit_distance_osa.pyx

@@ -98,6 +98,29 @@ def get_all_paths(
         python_paths.append(python_path)
     return python_paths
 
+def apply_editops(src, dst, editops):
+    src_idx = 0
+    s = ""
+    for op in editops:
+        while src_idx < op.src_idx:
+            s += src[src_idx]
+            src_idx += 1
+        if op.name == EditopName.INSERT:
+            s += dst[op.dst_idx]
+        elif op.name == EditopName.DELETE:
+            src_idx += 1
+        elif op.name == EditopName.REPLACE:
+            s += dst[op.dst_idx]
+            src_idx += 1
+        elif op.name == EditopName.SWAP:
+            s += dst[op.dst_idx]
+            s += dst[op.dst_idx + 1]
+            src_idx += 2
+    while src_idx < len(src):
+        s += src[src_idx]
+        src_idx += 1
+    return s
+
 
 def print_all_paths(
     str a,

tests/tests_osa.py

@@ -1,6 +1,7 @@
 import unittest
 
 from editdistance.osa import (
+    apply_editops,
     compute_distance,
     get_all_paths,
 )
@@ -22,6 +23,28 @@
     ("entirely different", "cab", "axb", 2),
 ]
 
+EDITOPS_TRANSFORM_TEST_CASES = [
+    ("abc", "acb"),
+    ("kitten", "sitting"),
+    ("flaw", "lawn"),
+    ("", "abc"),
+    ("abc", ""),
+    ("abcdef", "azced"),
+    ("a", "a"),
+    ("a", ""),
+    ("", ""),
+    ("banana", "ban"),
+    ("intention", "execution"),
+    ("gumbo", "gambol"),
+    ("sunday", "saturday"),
+    ("ca", "abc"),
+    ("abcdef", "fedcba"),
+    ("racecar", "racecar"),
+    ("spelling", "spilling"),
+    ("distance", "instance"),
+    ("book", "back"),
+]
+
 
 class TestOsaDistance(unittest.TestCase):
     def test_compute_distance(self):
@@ -49,3 +72,12 @@ def test_get_all_paths(self):
             ):
                 paths = get_all_paths(source, target)
                 self.assertEqual(len(paths), expected_num_paths)
+
+    def test_editops_transform(self):
+        for src, dst in EDITOPS_TRANSFORM_TEST_CASES:
+            with self.subTest(src=src, dst=dst):
+                paths = get_all_paths(src, dst)
+                self.assertTrue(paths, f"No paths found for {src} -> {dst}")
+                for path in paths:
+                    result = apply_editops(src, dst, path)
+                    self.assertEqual(result, dst, f"Failed for {src} -> {dst} with path {path}")