[diff.cpp03.containers] (original) (raw)
Annex C (informative) Compatibility [diff]
C.6 C++ and ISO C++ 2003 [diff.cpp03]
C.6.12 [containers]: containers library [diff.cpp03.containers]
Affected subclause: [container.requirements]
Change: Complexity of size() member functions now constant.
Rationale: Lack of specification of complexity of size() resulted in divergent implementations with inconsistent performance characteristics.
Effect on original feature: Some container implementations that conform to C++ 2003 may not conform to the specified size() requirements in this revision of C++.
Adjusting containers such as std::list to the stricter requirements may require incompatible changes.
Affected subclause: [container.requirements]
Change: Requirements change: relaxation.
Rationale: Clarification.
Effect on original feature: Valid C++ 2003 code that attempts to meet the specified container requirements may now be over-specified.
Code that attempted to be portable across containers may need to be adjusted as follows:
- not all containers provide size(); use empty() instead of size() == 0;
- not all containers are empty after construction (array);
- not all containers have constant complexity for swap() (array).
Affected subclause: [container.requirements]
Change: Requirements change: default constructible.
Rationale: Clarification of container requirements.
Effect on original feature: Valid C++ 2003 code that attempts to explicitly instantiate a container using a user-defined type with no default constructor may fail to compile.
Affected subclauses: [sequence.reqmts] and [associative.reqmts]
Change: Signature changes: from void return types.
Rationale: Old signature threw away useful information that may be expensive to recalculate.
Effect on original feature: The following member functions have changed:
- erase(iter) for set, multiset, map, multimap
- erase(begin, end) for set, multiset, map, multimap
- insert(pos, num, val) for vector, deque, list, forward_list
- insert(pos, beg, end) for vector, deque, list, forward_list
Valid C++ 2003 code that relies on these functions returning void(e.g., code that creates a pointer to member function that points to one of these functions) will fail to compile with this revision of C++.
Affected subclauses: [sequence.reqmts] and [associative.reqmts]
Change: Signature changes: from iterator to const_iteratorparameters.
Rationale: Overspecification.
Effect on original feature: The signatures of the following member functions changed from taking aniterator to taking a const_iterator:
- insert(iter, val) for vector, deque, list,set, multiset, map, multimap
- insert(pos, beg, end) for vector, deque, list,forward_list
- erase(begin, end) for set, multiset, map, multimap
- all forms of list::splice
- all forms of list::merge
Valid C++ 2003 code that uses these functions may fail to compile with this revision of C++.
Affected subclauses: [sequence.reqmts] and [associative.reqmts]
Change: Signature changes: resize.
Rationale: Performance, compatibility with move semantics.
Effect on original feature: For vector, deque, and listthe fill value passed to resize is now passed by reference instead of by value, and an additional overload of resize has been added.
Valid C++ 2003 code that uses this function may fail to compile with this revision of C++.