Using local classes with STL algorithms

by

It’s explicitly forbidden by the C++98/03 standard.

C++11 remove that restriction.

To be more complete :

The restrictions on types that are
used as template parameters are listed
in article 14.3.1 of the C++03 (and
C++98) standard:

A local type, a type with no linkage,
an unnamed type or a type compounded
from any of these types shall not be
used as a template-argument for a
template type-parameter.

template <class T> class Y { /* ... */  }; 
void func() {   
      struct S { /* ... */ }; //local class   
      Y< S > y1; // error: local type used as template-argument  
      Y< S* > y2; // error: pointer to local type used as template-argument }

Source and more details : http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=420

To sum up, the restriction was a mistake that would have been fixed sooner if the standard was evolving faster…

That said today most last versions of common compilers does allow it, along with providing lambda expressions.

More Related Contents:

  1. STL algorithms: Why no additional interface for containers (additional to iterator pairs)?
  2. What is the easiest way to initialize a std::vector with hardcoded elements?
  3. How do I specify a pointer to an overloaded function?
  4. C++ std::set update is tedious: I can’t change an element in place
  5. How to overload std::swap()
  6. Initializing a static std::map in C++
  7. Alternative to vector
  8. How do I sort a vector of pairs based on the second element of the pair?
  9. Is there any real risk to deriving from the C++ STL containers?
  10. maximum value of int
  11. How do I remove an item from a stl vector with a certain value?
  12. Why is template argument deduction disabled with std::forward?
  13. Is the order of iterating through std::map known (and guaranteed by the standard)?
  14. How to get a random element from a C++ container?
  15. c++ sort keeping track of indices [duplicate]
  16. Why can’t I write to a string literal while I *can* write to a string object?
  17. Multidimensional std::array [duplicate]
  18. Reorder vector using a vector of indices [duplicate]
  19. How to choose between map and unordered_map?
  20. Advantages of std::for_each over for loop
  21. C++ equivalent of StringBuffer/StringBuilder?
  22. Does std::stack expose iterators?
  23. Why does a push_back on an std::list change a reverse iterator initialized with rbegin?
  24. How to downsize std::vector?
  25. C++ convert vector to vector
  26. Why is the STL so heavily based on templates instead of inheritance?
  27. Using std::map where V has no usable default constructor
  28. How can I make the map::find operation case insensitive?
  29. Comparing 3 modern c++ ways to convert integral values to strings
  30. list of polymorphic objects

Leave a Comment