Function display_utils::join_format

pub fn join_format<I, C, J>(iterator: I, callback: C, joiner: J) -> impl Display where
    I: IntoIterator,
    I::IntoIter: Clone,
    C: Fn(I::Item, &mut Formatter<'_>) -> Result,
    J: Display, 

Concatenate iterator elements, separating each element pair with a given joiner, where each iterator element can be formatted using a callback.

The callback must be Fn and the iterator must be cloneable, because Display objects may be printed multiple times.

let strings = &["hello", "wonderful", "world"];

let output = join_format(
    strings.iter().enumerate(),
    |(i, string), f| write!(f, "{}={}", i, string),
    ", ",
);
assert_eq!(output.to_string(), "0=hello, 1=wonderful, 2=world");