How is it useful? It’s useful when you need a copy of *this – for example, when *this itself is no longer valid by the time the lambda is evaluated. How is it different from capturing this? It makes a copy of the object, so that when the lambda is evaluated, its this pointer refers … Read more
The entire reason lambda exists is that it’s an expression.1 If you want something that’s like lambda but is a statement, that’s just def. Python expressions cannot contain statements. This is, in fact, fundamental to the language, and Python gets a lot of mileage out of that decision. It’s the reason indentation for flow control … Read more
No. The function objects generated by lambda behave exactly like those generated by def. They do not execute any faster. (Also, inline in modern C++ is no longer a directive telling the compiler to inline a function, and has very little to do with inlining.) If you want, you can take a look at the … Read more
This is done in order to make sure that connection object outlives the asynchronous operation: as long as the lambda is alive (i.e. the async. operation is in progress), the connection instance is alive as well.
But now that has me thinking — did I do this correctly? Yes you did. Is there a better way in C++11 or C++14 to tell the compiler that I want it to immediately invoke a lambda I’ve written? Not that I know of. A lambda is also just a function object, so you need … Read more
It’s not desirable in the general case. (Note that it’s quite easy for std::function<T(A)> to specify what e.g. argument_type is: it’s just A! It’s available in the type definition.) It would be possible to require each and every function object type to specify its argument types, and in turn mandate that the closure types generated … Read more
Lambda functions are invoked by actually passing captured parameters to the function. value is equal to 0 at the point where the lambda is defined (and value is captured). Since you are capturing by value, it doesn’t matter what you do to value after the capture. If you had captured value by reference, then you … Read more
f = anotherdecorator(lambda x: x * 2)
The difference between a captured argument and a passing argument could be seen with an analogy. Consider the following function object: struct Capture { int &i; int const j; public: Capture(int &_i, int &_j) : i(_i), j(_j) {} int operator()(int const a, int const b) { i *= j; return a * b; } }; … Read more