// learns to remove input suffixes.

static class LRemoveInputSuffix extends LearnerImpl {
  static boolean debug;
  String suffix;
  static boolean failFast = false;
  
  public void processInOut(Object _in, Object _out) {
    String in = (String) _in, out = (String) _out;
    if (!in.startsWith(out)) fail();
    suffix = overwrite(suffix, in.substring(out.length()));
  }

  public String processIn(Object _in) {
    String in = (String) _in;
    if (!in.endsWith(suffix)) if (failFast) fail(); else return in;
    return in.substring(0, in.length()-suffix.length());
  }
}

Began life as a copy of #1000492