Rust Iteration Utilities

util_iter.rs

use core::fmt;

/// Folds an iterator with a spacer.
pub fn fold_iter_with_spacer<I, F, S, T, E>(
    iter: I,
    init: T,
    mut f: F,
    mut spacer: S,
) -> Option<Result<T, E>>
where
    I: IntoIterator,
    F: FnMut(I::Item) -> Result<T, E>,
    S: FnMut() -> Result<T, E>,
{
    let mut iter = iter.into_iter();
    iter.next()
        .map(move |n| f(n).and(iter.try_fold(init, move |_, t| spacer().and(f(t)))))
}

/// Formats an iterator pointwise with a spacer.
pub fn format_iter_with_spacer<I, FT, FS>(
    iter: I,
    f: &mut fmt::Formatter,
    format: FT,
    format_spacer: FS,
) -> fmt::Result
where
    I: IntoIterator,
    FT: Fn(I::Item, &mut fmt::Formatter) -> fmt::Result,
    FS: Fn(&mut fmt::Formatter) -> fmt::Result,
{
    let mut iter = iter.into_iter();
    iter.next()
        .map(move |n| {
            format(n, f).and(iter.try_fold((), move |_, t| format_spacer(f).and(format(t, f))))
        })
        .unwrap_or(Ok(()))
}