C++: Moving from C++03 to C++11

Bjarne Stroustrup, the creator of C++, said recently that C++11 “feels like a new language — the pieces just fit together better.”

Indeed, core C++11 has changed significantly.

New features include:

• lambda expressions
• automatic type deduction of objects
• uniform initialization syntax 
• delegating constructors
• deleted and defaulted function declarations
• nullptr
• rvalue references

An example: suppose that v is a vector:

vector<int> v(10,10); //10 ints with value 10

and we want to call a function foo on each element of v. In C++03, we might do so this way:

for (vector::size_type i = 0; i != v.size(); ++i)
      foo(v[i]);

A more sophisticated style is to use an iterator, thereby avoiding what would otherwise be a dependency on the ability to use subscripts:

for (vector::iterator it = v.begin(); it != v.end(); ++it)
      foo(*it);

If we are to write this code fragment to take advantage of C++11, we might well do so differently. For example, we might write the first example this way:

for (decltype(v.size()) i = 0; i != v.size(); ++i)
      foo(v[i]);

but we would be more likely to write something like this:

for (auto it = v.begin(); it != v.end(); ++it)
      foo(it);

or even like this:

for (auto x: v)
      foo(x)

Looks like we moving towards interpreted languages…

Sources:

• Andrew Koenig (Dr. Dobb’s Bloggers)
• Danny Kalev (Smartbear blog)