How can I store function pointers in an array? [duplicate]

问题:

This question already has an answer here:

• Accepting named functions vs. unboxed closures : distinct types issues 1 answer

How do you stick functions (or function pointers) into an array for testing purposes?

fn foo() -> isize { 1 } fn bar() -> isize { 2 }  fn main() {     let functions = vec![foo, bar];     println!("foo() = {}, bar() = {}", functions[0](), functions[1]()); } 

This code in the Rust playground

This is the error code I get:

error: mismatched types:  expected `fn() -> isize {foo}`,     found `fn() -> isize {bar}` (expected fn item,     found a different fn item) [E0308]      let functions = vec![foo, bar];                               ^~~ 

Rust is treating my functions (values) as different types despite having the same signatures, which I find surprising.

回答1:

At some point recently, each function was given its own, distinct type for... reasons that I don't recall. Upshot is that you need to give the compiler a hint (note the type on functions):

fn foo() -> isize {     1 } fn bar() -> isize {     2 } fn main() {     let functions: Vec isize> = vec![foo, bar];     println!("foo() = {}, bar() = {}", functions[0](), functions[1]()); } 

You can also do this like so:

let functions = vec![foo as fn() -> isize, bar]; 

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