WebThere are two easy solutions in safe rust. First, use Vec::split_at_mut.Then you can get a mutable reference to both outer[i] and outer[j].. Otherwise, Vec implements Default so you can use std::mem::take to take outer[i] and outer[j] out of the vector without reallocating. When you want to put them back, use std::mem::replace.. Or use std::mem::swap. Web// Thus, std::mem_fn is a better alternative: auto p2 = std::mem_fn(& S ::two_args); p2 ( s, 1, 2); // auto pd = std::mem_fun (&S::data); // Error: pointers to data members are not supported. // Use std::mem_fn instead: auto pd = std::mem_fn(& S ::data); std::cout << "s.data = " << pd ( s) << '\n'; } Possible output:

std::mem - Rust

WebJul 15, 2024 · And even these standard library methods do it this way; take a look at the implementation of mem::replace, it’s really quite straightforward code. use std::ptr; pub fn replace (dest: &mut T, src: T) -> T { // SAFETY: We read from `dest` but directly write `src` into it afterwards, // such that the old value is not duplicated. gregg\u0027s heating and air

std::replace, std::replace_if - cppreference.com

WebMay 25, 2024 · Both std::mem::replace (or swap ) and splitting is necessary to do it. If you lack any one of them, it isn't possible. It turns out that Option::take () is a viable alternative to the std::mem functions here: Webmem::take lets us swap out the value, replacing it with it's default value, and returning the previous value. For String, the default value is an empty String, which does not need to allocate. As a result, we get the original name as an … WebFeb 13, 2024 · std::mem::replace looks like a power tool. I hope I can understand it well enough to use it one day. Option::take uses std::mem::replace internally . The way to think of these is that Rust “doesn’t understand” a logical replacement of a value when it’s done in multiple steps. The doc for mem::replace puts this example forward: gregg\u0027s ranch dressing ingredients