text: /*
   * Copyright 2019 Denis Yaroshevskiy
   *
   * 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.
   */
  
  #ifndef ALGO_ADVANCE_UP_TO_H
  #define ALGO_ADVANCE_UP_TO_H
  
  #include <algorithm>
  
  #include "algo/type_functions.h"
  
  namespace algo {
  
  template <typename I>
  // require InputIterator<I>
  constexpr void advance_up_to(I& f, I l, DifferenceType<I>& n) {
    if constexpr (RandomAccessIterator<I>) {
      DifferenceType<I> actual_n = std::min(n, l - f);
      f += actual_n;
      n -= actual_n;
    } else {
      while (f != l && n) {
        ++f;
        --n;
      }
    }
  }
  
  }  // namespace algo
  
  #endif  // ALGO_ADVANCE_UP_TO_H
  