An anonymous function is just a function that has no name; nothing more. A closure is a function that captures the state of the surrounding environment. An anonymous function does not necessarily need to create a closure, and a closure is not created only for anonymous functions. Consider this hypothetical counter-example. Consider a language Foo … Read more
Complementing the existing answer with some more code for demonstration purposes: Unboxed closure Use a generic type: struct Foo<F> where F: Fn(usize) -> usize, { pub foo: F, } impl<F> Foo<F> where F: Fn(usize) -> usize, { fn new(foo: F) -> Self { Self { foo } } } fn main() { let foo = … Read more
Chris Lattner wrote on the developer forums: This is a feature we intentionally do not want to support. There are a variety of things that will cause pointer equality of functions (in the swift type system sense, which includes several kinds of closures) to fail or change depending on optimization. If “===” were defined on … Read more
Consider a function that takes one argument, a simple closure that takes no argument: func f(pred: () -> Bool) { if pred() { print(“It’s true”) } } To call this function, we have to pass in a closure f(pred: {2 > 1}) // “It’s true” If we omit the braces, we are passing in an … Read more