Bind Vs Lambda?

Question

I have a question about which style is preferred: std::bind Vs lambda in C++0x. I know that they serve -somehow- different purposes but lets take an example of intersecting functionality.

Using lambda:

uniform_int<> distribution(1, 6); mt19937 engine; // lambda style auto dice = [&]() { return distribution(engine); }; 

Using bind:

uniform_int<> distribution(1, 6); mt19937 engine; // bind style auto dice = bind(distribution, engine); 

Which one should we prefer? why? assuming more complex situations compared to the mentioned example. i.e. What are the advantages/disadvantages of one over the other?

Answer 1

C++0x lambdas are monomorphic, while bind can be polymorphic. You cannot have something like

auto f = [](auto a, auto b) { cout << a << ' ' << b; } f("test", 1.2f); 

a and b must have known types. On the other hand, tr1/boost/phoenix/lambda bind allows you to do this:

struct foo {   typedef void result_type;    template < typename A, typename B >   void operator()(A a, B b)   {     cout << a << ' ' << b;   } };  auto f = bind(foo(), _1, _2); f("test", 1.2f); // will print "test 1.2" 

Note that the types A and B are not fixed here. Only when f is actually used these two will be deduced.