When you write int fun2(int fun()), the parameter int fun() converts into int (*fun)(), it becomes exactly equivalent to this: int fun2(int (*fun)()); A more famiiar conversion happens in case of array when you declare it as function parameter. For example, if you’ve this: int f(int a[100]); Even here the parameter type converts into int*, … Read more
Your function binsearch takes a function pointer as argument. A lambda and a function pointer are different types: a lambda may be considered as an instance of a struct implementing operator(). Note that stateless lambdas (lambdas that don’t capture any variable) are implicitly convertible to function pointer. Here the implicit conversion doesn’t work because of … Read more
Note that there is a difference between equality and identity. The operators == and != in Go1 are comparing the values for equivalence (except when comparing channels), not for identity. Because these operators are trying not to mix equality and identity, Go1 is more consistent than pre-Go1 in this respect. Function equality is different from … Read more
Start with your declaration for f1: int (*f1)(float); You want f2 to be a pointer to a function returning f1, so substitute f1 in the declaration above with the declaration for f2: int (* f1 )(float); | +—–+—–+ | | v v int (*(*f2)(double))(float); The declaration reads as f2 — f2 *f2 — is a … Read more
No, there is no difference, since function can be implicitly converted to pointer to function. Relevant quote from standard (N3376 4.3/1). An lvalue of function type T can be converted to a prvalue of type “pointer to T.” The result is a pointer to the function.
arr //arr arr [] //is an array (so index it) * arr [] //of pointers (so dereference them) (* arr [])() //to functions taking nothing (so call them with ()) void (* arr [])() //returning void so your answer is void (* arr [])() = {}; But naturally, this is a bad practice, just use … Read more
You can’t. You either pass a pointer to a static method or Parent has to accept also a pointer to the object. You might want to look at boost::bind and boost::function for that: #include <boost/bind.hpp> #include <boost/function.hpp> struct Y { void say(void) { std::cout << “hallo!”;} boost::function<void()> getFunc() { return boost::bind(&Y::say, this); } }; struct … Read more
As others have noted, it is certainly possible to implement this in C. Not only is it possible, it is a fairly common mechanism. The most commonly used example is probably the file descriptor interface in UNIX. A read() call on a file descriptor will dispatch to a read function specific to the device or … Read more
In the most normal situation, you can pretty much think of struct A { int i; int foo() { return i; } }; A a; a.foo(); as struct A { int i; }; int A_foo( A* this ) { return this->i; }; A a; A_foo(&a); (Starting to look like C, right?) So you would think … Read more
I’m assuming that the closure argument is a context ‘cookie’ for the use of the callback to get appropriate context. This is a acomon idiom for callback functions, and seems to be what’s going on based on the snippets you’ve provided (but I don’t know for sure, as I don’t know anything about kcache_create() except … Read more