itertools/
format.rs

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1use std::fmt;
2use std::cell::RefCell;
3
4/// Format all iterator elements lazily, separated by `sep`.
5///
6/// The format value can only be formatted once, after that the iterator is
7/// exhausted.
8///
9/// See [`.format_with()`](../trait.Itertools.html#method.format_with) for more information.
10pub struct FormatWith<'a, I, F> {
11    sep: &'a str,
12    /// FormatWith uses interior mutability because Display::fmt takes &self.
13    inner: RefCell<Option<(I, F)>>,
14}
15
16/// Format all iterator elements lazily, separated by `sep`.
17///
18/// The format value can only be formatted once, after that the iterator is
19/// exhausted.
20///
21/// See [`.format()`](../trait.Itertools.html#method.format)
22/// for more information.
23#[derive(Clone)]
24pub struct Format<'a, I> {
25    sep: &'a str,
26    /// Format uses interior mutability because Display::fmt takes &self.
27    inner: RefCell<Option<I>>,
28}
29
30pub fn new_format<'a, I, F>(iter: I, separator: &'a str, f: F) -> FormatWith<'a, I, F>
31    where I: Iterator,
32          F: FnMut(I::Item, &mut FnMut(&fmt::Display) -> fmt::Result) -> fmt::Result
33{
34    FormatWith {
35        sep: separator,
36        inner: RefCell::new(Some((iter, f))),
37    }
38}
39
40pub fn new_format_default<'a, I>(iter: I, separator: &'a str) -> Format<'a, I>
41    where I: Iterator,
42{
43    Format {
44        sep: separator,
45        inner: RefCell::new(Some(iter)),
46    }
47}
48
49impl<'a, I, F> fmt::Display for FormatWith<'a, I, F>
50    where I: Iterator,
51          F: FnMut(I::Item, &mut FnMut(&fmt::Display) -> fmt::Result) -> fmt::Result
52{
53    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
54        let (mut iter, mut format) = match self.inner.borrow_mut().take() {
55            Some(t) => t,
56            None => panic!("FormatWith: was already formatted once"),
57        };
58
59        if let Some(fst) = iter.next() {
60            try!(format(fst, &mut |disp: &fmt::Display| disp.fmt(f)));
61            for elt in iter {
62                if self.sep.len() > 0 {
63
64                    try!(f.write_str(self.sep));
65                }
66                try!(format(elt, &mut |disp: &fmt::Display| disp.fmt(f)));
67            }
68        }
69        Ok(())
70    }
71}
72
73impl<'a, I> Format<'a, I>
74    where I: Iterator,
75{
76    fn format<F>(&self, f: &mut fmt::Formatter, mut cb: F) -> fmt::Result
77        where F: FnMut(&I::Item, &mut fmt::Formatter) -> fmt::Result,
78    {
79        let mut iter = match self.inner.borrow_mut().take() {
80            Some(t) => t,
81            None => panic!("Format: was already formatted once"),
82        };
83
84        if let Some(fst) = iter.next() {
85            try!(cb(&fst, f));
86            for elt in iter {
87                if self.sep.len() > 0 {
88                    try!(f.write_str(self.sep));
89                }
90                try!(cb(&elt, f));
91            }
92        }
93        Ok(())
94    }
95}
96
97macro_rules! impl_format {
98    ($($fmt_trait:ident)*) => {
99        $(
100            impl<'a, I> fmt::$fmt_trait for Format<'a, I>
101                where I: Iterator,
102                      I::Item: fmt::$fmt_trait,
103            {
104                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
105                    self.format(f, fmt::$fmt_trait::fmt)
106                }
107            }
108        )*
109    }
110}
111
112impl_format!{Display Debug
113             UpperExp LowerExp UpperHex LowerHex Octal Binary Pointer}
itertools/format.rs

itertools/
format.rs
