What's the point in defaulting functions in C++11?

Question

C++11 adds the ability for telling the compiler to create a default implementation of any of the special member functions. While I can see the value of deleting a function,

Answer 1

Those examples from Stroustrup's website might help you understand the point:

defaulted and deleted functions -- control of defaults

The common idiom of "prohibiting copying" can now be expressed directly:

class X {
  // ...

  X& operator=(const X&) = delete;    // Disallow copying
  X(const X&) = delete;
};

Conversely, we can also say explicitly that we want to default copy behavior:

class Y {
  // ...
  Y& operator=(const Y&) = default;   // default copy semantics
  Y(const Y&) = default;

};

Being explicit about the default is obviously redundant, but comments to that effect and (worse) a user explicitly defining copy operations meant to give the default behavior are not uncommon. Leaving it to the compiler to implement the default behavior is simpler, less error-prone, and often leads to better object code. The "default" mechanism can be used for any function that has a default. The "delete" mechanism can be used for any function. For example, we can eliminate an undesired conversion like this:

struct Z {
  // ...

  Z(long long);     // can initialize with an long long
  Z(long) = delete; // but not anything less
};

Answer 2

For me its the disabling feature that will be useful, For most of the classes I currently create I disable copying & assignment - it will be nice to have a feature the compiler can recognise to do this, rather than depending on linker errors.