what happens when you modify an element of an std::set?

by

You should not edit the values stored in the set directly. I copied this from MSDN documentation which is somewhat authoritative:

The STL container class set is used
for the storage and retrieval of data
from a collection in which the values
of the elements contained are unique
and serve as the key values according
to which the data is automatically
ordered. The value of an element in a
set may not be changed directly.
Instead, you must delete old values
and insert elements with new values.

Why this is is pretty easy to understand. The set implementation will have no way of knowing you have modified the value behind its back. The normal implementation is a red-black tree. Having changed the value, the position in the tree for that instance will be wrong. You would expect to see all manner of wrong behaviour, such as exists queries returning the wrong result on account of the search going down the wrong branch of the tree.

More Related Contents:

  1. C++ std::set update is tedious: I can’t change an element in place
  2. How to update an existing element of std::set?
  3. How to check that an element is in a std::set?
  4. Does boost have a datatype for set operations that is simpler than the STL?
  5. Is the std::set iteration order always ascending according to the C++ specification?
  6. Erasing elements from a vector
  7. Why can’t I make a vector of references?
  8. Concise explanation of reference collapsing rules requested: (1) A& & -> A& , (2) A& && -> A& , (3) A&& & -> A& , and (4) A&& && -> A&&
  9. Why are Standard iterator ranges [begin, end) instead of [begin, end]?
  10. Why do I get the same sequence for every run with std::random_device with mingw gcc4.8.1?
  11. Using custom std::set comparator
  12. Nice way to append a vector to itself
  13. Why use non-member begin and end functions in C++11?
  14. std::fstream doesn’t create file
  15. A proper way to create a matrix in c++
  16. Why does C++ allow an integer to be assigned to a string?
  17. std::vector, default construction, C++11 and breaking changes
  18. Why is value taking setter member functions not recommended in Herb Sutter’s CppCon 2014 talk (Back to Basics: Modern C++ Style)?
  19. OpenMP set_num_threads() is not working
  20. std::vector iterator invalidation
  21. Non-copyable elements in vector
  22. How to pretty-print STL containers in GDB?
  23. How to make elements of vector unique? (remove non adjacent duplicates)
  24. How can I use Standard Library (STL) classes in my dll interface or ABI?
  25. How can i estimate memory usage of std::map?
  26. STL deque accessing by index is O(1)?
  27. Incrementing iterators: Is ++it more efficient than it++? [duplicate]
  28. what does `using std::swap` inside the body of a class method implementation mean?
  29. error for hash function of pair of ints
  30. Why does (i|o)fstream take a const char* parameter for a file name?

Leave a Comment