text: // Copyright 2005-2020 Google LLC
  //
  // Licensed under the Apache License, Version 2.0 (the 'License');
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //     http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an 'AS IS' BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  //
  // See www.openfst.org for extensive documentation on this weighted
  // finite-state transducer library.
  //
  // Two DFAs are equivalent iff their exit status is zero.
  
  #include <cstring>
  #include <memory>
  #include <string>
  
  #include <fst/flags.h>
  #include <fst/log.h>
  #include <fst/script/equivalent.h>
  #include <fst/script/getters.h>
  #include <fst/script/randequivalent.h>
  
  DECLARE_double(delta);
  DECLARE_bool(random);
  DECLARE_int32(max_length);
  DECLARE_int32(npath);
  DECLARE_uint64(seed);
  DECLARE_string(select);
  
  int fstequivalent_main(int argc, char **argv) {
    namespace s = fst::script;
    using fst::RandGenOptions;
    using fst::script::FstClass;
  
    std::string usage =
        "Two DFAs are equivalent iff the exit status is zero.\n\n"
        "  Usage: ";
    usage += argv[0];
    usage += " in1.fst in2.fst\n";
  
    std::set_new_handler(FailedNewHandler);
    SET_FLAGS(usage.c_str(), &argc, &argv, true);
    if (argc != 3) {
      ShowUsage();
      return 1;
    }
  
    const std::string in1_name = strcmp(argv[1], "-") == 0 ? "" : argv[1];
    const std::string in2_name = strcmp(argv[2], "-") == 0 ? "" : argv[2];
  
    if (in1_name.empty() && in2_name.empty()) {
      LOG(ERROR) << argv[0] << ": Can't take both inputs from standard input";
      return 1;
    }
  
    std::unique_ptr<FstClass> ifst1(FstClass::Read(in1_name));
    if (!ifst1) return 1;
  
    std::unique_ptr<FstClass> ifst2(FstClass::Read(in2_name));
    if (!ifst2) return 1;
  
    if (!FST_FLAGS_random) {
      bool result = s::Equivalent(*ifst1, *ifst2, FST_FLAGS_delta);
      if (!result) VLOG(1) << "FSTs are not equivalent";
      return result ? 0 : 2;
    } else {
      s::RandArcSelection ras;
      if (!s::GetRandArcSelection(FST_FLAGS_select, &ras)) {
        LOG(ERROR) << argv[0] << ": Unknown or unsupported select type "
                   << FST_FLAGS_select;
        return 1;
      }
      const RandGenOptions<s::RandArcSelection> opts(
          ras, FST_FLAGS_max_length);
      bool result = s::RandEquivalent(*ifst1, *ifst2, FST_FLAGS_npath,
                                      opts, FST_FLAGS_delta,
                                      FST_FLAGS_seed);
      if (!result) VLOG(1) << "FSTs are not equivalent";
      return result ? 0 : 2;
    }
  }
  