When Should You Prefer `std::bind` Over Lambdas in C 14?

Why Consider std::bind Over Lambdas in C 14?

C 14 introduced powerful lambda expressions, prompting some to question the continued relevance of std::bind. While lambdas offer concise syntax, std::bind maintains its utility in certain scenarios.

Unmovable Captured Variables:
In C 11, lambdas can only capture lvalue variables, while bind allows moving variables. Through bind, you can write the following code:

auto f1 = std::bind(f, 42, _1, std::move(v));

Capture expression:
lambda cannot capture expressions directly. Instead, bind allows writing like this:

auto f1 = std::bind(f, 42, _1, a + b);

Function object overloading parameters:
In C 14, lambdas can solve this problem through type inference, and bind here Still a blast in the scene.

Unable to pass parameters:
Ideally, the bind that needs to use perfect forwarding can be written like the following code:

auto f1 = [=](auto&amp;&amp; arg) { f(42, std::forward<decltype(arg)>(arg)); };

However Instead, bind blocks it to the following form:

auto f1 = std::bind(std::declval<decltype(f)>(), 42, _1);
auto f2 = std::bind(f, 42, std::declval<decltype(arg)>(), std::placeholders::_2);

Disadvantages of bind:

• Bind names can lead to ambiguity in overloaded functions.
• Functions are more likely to be inlined when using bind than lambda.

Despite this, bind still has its advantages. It only produces a function object type, whereas lambda may produce a unique type for each function. Ultimately, choosing bind or lambda depends on specific use cases and trade-offs.

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