Pass async functions with `BoxFuture`

box_future.rs

// [dependencies]
// futures = "*"
// async-std = "*"

use futures::{future::BoxFuture, FutureExt};
use async_std::task;


fn main() {
    let mut functions: Vec<fn(usize) -> BoxFuture<'static, usize>> = Vec::new();

    functions.push( |x| { add_one(x).boxed() } );
    functions.push( |x| { add_two(x).boxed() } );
    functions.push( |x| { add_three(x).boxed() } );

    let mut j = 0;
    task::block_on(async {
        for f in functions.drain(..) {
            j = f(j).await;
            dbg!(j);
        }
    });
}

async fn add_one(x: usize) -> usize {
    x+1
}
async fn add_two(x: usize) -> usize {
    x+2
}
async fn add_three(x: usize) -> usize {
    x+3
}