1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114

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()`](../trait.Itertools.html#method.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()`](../trait.Itertools.html#method.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<'a, I, F>(iter: I, separator: &'a str, f: F) -> FormatWith<'a, 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<'a, I>(iter: I, separator: &'a str) -> Format<'a, 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))?;
            for elt in iter {
                if self.sep.len() > 0 {

                    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)?;
            for elt in iter {
                if self.sep.len() > 0 {
                    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}