Function fmty::join_map_once

pub fn join_map_once<I, S, R, F>(
    iter: I,
    sep: S,
    f: F
) -> JoinMapOnce<I::IntoIter, S, F>where
    I: IntoIterator,
    F: Fn(I::Item) -> R,

Concatenates mapped Iterator results with a separator between each, at most once.

This is a non-Clone alternative to join_map(). It uses interior mutability to take ownership of the iterator in the first call to Display::fmt(). As a result, JoinMapOnce does not implement Sync.

Examples

let value = fmty::join_map_once(["hola", "mundo"], " ", fmty::to_ascii_uppercase);
assert_eq!(value.to_string(), "HOLA MUNDO");

assert_eq!(value.to_string(), "");