Why use iterators instead of array indices?

by

The first form is efficient only if vector.size() is a fast operation. This is true for vectors, but not for lists, for example. Also, what are you planning to do within the body of the loop? If you plan on accessing the elements as in

T elem = some_vector[i];

then you’re making the assumption that the container has operator[](std::size_t) defined. Again, this is true for vector but not for other containers.

The use of iterators bring you closer to container independence. You’re not making assumptions about random-access ability or fast size() operation, only that the container has iterator capabilities.

You could enhance your code further by using standard algorithms. Depending on what it is you’re trying to achieve, you may elect to use std::for_each(), std::transform() and so on. By using a standard algorithm rather than an explicit loop you’re avoiding re-inventing the wheel. Your code is likely to be more efficient (given the right algorithm is chosen), correct and reusable.

More Related Contents:

  1. What is an iterator’s default value?
  2. Do STL iterators guarantee validity after collection was changed?
  3. How can I use std::maps with user-defined types as key?
  4. Why are Standard iterator ranges [begin, end) instead of [begin, end]?
  5. Why isn’t vector a STL container?
  6. What’s the best way to iterate over two or more containers simultaneously
  7. Removing item from vector while iterating?
  8. comparing iterators from different containers
  9. Why use non-member begin and end functions in C++11?
  10. How are iterators and pointers related?
  11. What’s faster, iterating an STL vector with vector::iterator or with at()?
  12. Copy map values to vector in STL [duplicate]
  13. Custom Iterator in C++
  14. Why is “!=” used with iterators instead of “
  15. Why does storing references (not pointers) in containers in C++ not work?
  16. Can std::begin work with array parameters and if so, how?
  17. std::vector iterator invalidation
  18. Iterate through a C++ Vector using a ‘for’ loop
  19. Checking if an iterator is valid
  20. Why does a push_back on an std::list change a reverse iterator initialized with rbegin?
  21. What happens if you increment an iterator that is equal to the end iterator of an STL container
  22. Need iterator when using ranged-based for loops
  23. Are const_iterators faster?
  24. How to check that the passed Iterator is a random access iterator?
  25. Incrementing iterators: Is ++it more efficient than it++? [duplicate]
  26. General use cases for C++ containers
  27. How to increment an iterator by 2?
  28. Types of iterator : Output vs. Input vs. Forward vs. Random Access Iterator
  29. iterator for 2d vector
  30. How can I copy one map into another using std::copy?

Leave a Comment