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    <p>I've never heard of the "explicit is better than implicit rule" rule, and I don't agree with it. There are cases where it's true, of course, but also plenty of cases where it isn't. That's why 0x is adding type inference with the <code>auto</code> keyword after all. (and why function template parameters are already inferred when possible) There are plenty of cases where implicit is preferable.</p> <p>I haven't really used C++ lambdas yet (other than poking around with the VC10 beta), but I'd go with the latter most of the time</p> <pre><code>std::for_each(xs.begin(), xs.end(), [&amp;](int x) { sum += x }); </code></pre> <p>My reasoning? Why not do it? It's convenient. It works. And it's easier to maintain. I don't have to update the capture list when I modify the body of the lambda. Why should I be explicit about something the compiler knows better than me? The compiler can figure out the capture list based on what's actually used.</p> <p>As for capture by reference vs value? I'd apply the same rules as I do for regular functions. If you need reference semantics, capture by reference. If you need copy semantics, do that. If either will do, prefer value for smallish types, and reference if copying is expensive.</p> <p>It doesn't seem different from the choice you have to make when designing a regular function.</p> <p>I should probably read up on the specs for lambdas, but isn't the main reason for explicit capture lists so that you can capture some variables by value and others by reference?</p>
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    1. COThere's no explicit rationale for it, but yes, it is something that's only possible with a capture list.
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    2. CORegarding "compiler knows better than me" - compiler doesn't know the lifetime of lambda. If you would have assigned a `[&]` lambda to `std::function` in outer scope, it will happily let you do so and then leave the lambda scope - but, of course, all references in the lambda will be invalid when you actually call it...
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    3. CO"Explicit is better than implicit" is from The Zen of Python (http://www.python.org/dev/peps/pep-0020/), but that thing isn't really specific to Python.
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