src/iter.rs

use std::iter::Peekable;
use std::ops::Deref;

pub struct Delimited<I: Iterator> {
    is_first: bool,
    iter: Peekable<I>,
}

pub trait IterDelimited: Iterator + Sized {
    fn delimited(self) -> Delimited<Self> {
        Delimited {
            is_first: true,
            iter: self.peekable(),
        }
    }
}

impl<I: Iterator> IterDelimited for I {}

pub struct IteratorItem<T> {
    value: T,
    pub is_first: bool,
    pub is_last: bool,
}

impl<I: Iterator> Iterator for Delimited<I> {
    type Item = IteratorItem<I::Item>;

    fn next(&mut self) -> Option<Self::Item> {
        let item = IteratorItem {
            value: self.iter.next()?,
            is_first: self.is_first,
            is_last: self.iter.peek().is_none(),
        };
        self.is_first = false;
        Some(item)
    }
}

impl<T> Deref for IteratorItem<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.value
    }
}