extended the ed app

app/ed.py

@@ -131,6 +131,21 @@ class Ed:
             self.dirty = True
           self.current_line = idx
 
+        elif cmd_char == 'c':
+          if not self.buffer:
+            print("?")
+            continue
+          del self.buffer[start-1 : end]
+          idx = start - 1
+          while True:
+            line = input("")
+            if line == ".":
+              break
+            self.buffer.insert(idx, line)
+            idx += 1
+            self.dirty = True
+          self.current_line = idx
+
         elif cmd_char == 'd':
           if not self.buffer:
             print("?")
@@ -139,6 +154,25 @@ class Ed:
           self.current_line = min(start, len(self.buffer))
           self.dirty = True
 
+        elif cmd_char == 's':
+          if not self.buffer or not params:
+            print("?")
+            continue
+          # Simple s/old/new/ parser
+          sep = params[0]
+          parts = params.split(sep)
+          if len(parts) < 3:
+            print("?")
+            continue
+          old, new = parts[1], parts[2]
+          start = max(1, start)
+          end = min(len(self.buffer), end)
+          for i in range(start - 1, end):
+            if old in self.buffer[i]:
+              self.buffer[i] = self.buffer[i].replace(old, new)
+              self.dirty = True
+          self.current_line = end
+
         elif cmd_char == 'w':
           target = params if params else self.filename
           if not target: