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use std::fmt;
use std::cell::RefCell;
pub struct Format<'a, I, F> {
sep: &'a str,
inner: RefCell<(I, F)>,
}
pub fn new_format<'a, I, F>(iter: I, separator: &'a str, f: F) -> Format<'a, I, F>
where I: Iterator,
F: FnMut(I::Item, &mut FnMut(&fmt::Display) -> fmt::Result) -> fmt::Result
{
Format {
sep: separator,
inner: RefCell::new((iter, f)),
}
}
impl<'a, I, F> fmt::Display for Format<'a, I, F>
where I: Iterator,
F: FnMut(I::Item, &mut FnMut(&fmt::Display) -> fmt::Result) -> fmt::Result
{
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
let mut cb = &mut |disp: &fmt::Display| write!(fmt, "{}", disp);
let (ref mut iter, ref mut format) = *&mut *self.inner.borrow_mut();
if let Some(fst) = iter.next() {
try!(format(fst, cb));
for elt in iter {
if self.sep.len() > 0 {
try!(cb(&self.sep));
}
try!(format(elt, cb));
}
}
Ok(())
}
}