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use std::fmt;
use std::cell::RefCell;
/// Format all iterator elements lazily, separated by `sep`.
///
/// The format value can only be formatted once, after that the iterator is
/// exhausted.
///
/// See [`.format_with()`](crate::Itertools::format_with) for more information.
#[derive(Clone)]
pub struct FormatWith<'a, I, F> {
sep: &'a str,
/// FormatWith uses interior mutability because Display::fmt takes &self.
inner: RefCell<Option<(I, F)>>,
}
/// Format all iterator elements lazily, separated by `sep`.
///
/// The format value can only be formatted once, after that the iterator is
/// exhausted.
///
/// See [`.format()`](crate::Itertools::format)
/// for more information.
#[derive(Clone)]
pub struct Format<'a, I> {
sep: &'a str,
/// Format uses interior mutability because Display::fmt takes &self.
inner: RefCell<Option<I>>,
}
pub fn new_format<I, F>(iter: I, separator: &str, f: F) -> FormatWith<'_, I, F>
where I: Iterator,
F: FnMut(I::Item, &mut dyn FnMut(&dyn fmt::Display) -> fmt::Result) -> fmt::Result
{
FormatWith {
sep: separator,
inner: RefCell::new(Some((iter, f))),
}
}
pub fn new_format_default<I>(iter: I, separator: &str) -> Format<'_, I>
where I: Iterator,
{
Format {
sep: separator,
inner: RefCell::new(Some(iter)),
}
}
impl<'a, I, F> fmt::Display for FormatWith<'a, I, F>
where I: Iterator,
F: FnMut(I::Item, &mut dyn FnMut(&dyn fmt::Display) -> fmt::Result) -> fmt::Result
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let (mut iter, mut format) = match self.inner.borrow_mut().take() {
Some(t) => t,
None => panic!("FormatWith: was already formatted once"),
};
if let Some(fst) = iter.next() {
format(fst, &mut |disp: &dyn fmt::Display| disp.fmt(f))?;
iter.try_for_each(|elt| {
if !self.sep.is_empty() {
f.write_str(self.sep)?;
}
format(elt, &mut |disp: &dyn fmt::Display| disp.fmt(f))
})?;
}
Ok(())
}
}
impl<'a, I> Format<'a, I>
where I: Iterator,
{
fn format<F>(&self, f: &mut fmt::Formatter, mut cb: F) -> fmt::Result
where F: FnMut(&I::Item, &mut fmt::Formatter) -> fmt::Result,
{
let mut iter = match self.inner.borrow_mut().take() {
Some(t) => t,
None => panic!("Format: was already formatted once"),
};
if let Some(fst) = iter.next() {
cb(&fst, f)?;
iter.try_for_each(|elt| {
if !self.sep.is_empty() {
f.write_str(self.sep)?;
}
cb(&elt, f)
})?;
}
Ok(())
}
}
macro_rules! impl_format {
($($fmt_trait:ident)*) => {
$(
impl<'a, I> fmt::$fmt_trait for Format<'a, I>
where I: Iterator,
I::Item: fmt::$fmt_trait,
{
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
self.format(f, fmt::$fmt_trait::fmt)
}
}
)*
}
}
impl_format!{Display Debug
UpperExp LowerExp UpperHex LowerHex Octal Binary Pointer}