Question

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Bind Vs Lambda?

My use of std::bind had dropped to 0 now that lambdas have gained wide support.

Are there any problems that std::bind is uniquely suited for over a lambda function?

Was there a compelling reason to keep std::bind in the standard once lambdas where added?

Answer 1

You can capture by value or by reference, and the problem is that capture by value really means ‘capture by copy’. This is a show stopper for a move-only type. So you can’t use a lambda to do the following:

struct foo { void bar() {} };

std::unique_ptr<foo> f { new foo };
auto bound = std::bind(&foo::bar, std::move(f));
static_assert( std::is_move_constructible<decltype(bound)>::value, "" );
bound();

IIRC the Standard Committee briefly considered allowing arbitrary expression inside a lambda capture list to solve this (which could look like [std::move(f)] { return f.bar(); }), but I don’t think there was a solid proposal and C++11 was already running late.

That and the restriction to monomorphic behaviour with lambdas are the deal breakers for me.