1 use std::fmt;
2 use 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.
10 #[derive(Clone)]
11 pub struct FormatWith<'a, I, F> {
12 sep: &'a str,
13 /// FormatWith uses interior mutability because Display::fmt takes &self.
14 inner: RefCell<Option<(I, F)>>,
15 }
16
17 /// Format all iterator elements lazily, separated by `sep`.
18 ///
19 /// The format value can only be formatted once, after that the iterator is
20 /// exhausted.
21 ///
22 /// See [`.format()`](../trait.Itertools.html#method.format)
23 /// for more information.
24 #[derive(Clone)]
25 pub struct Format<'a, I> {
26 sep: &'a str,
27 /// Format uses interior mutability because Display::fmt takes &self.
28 inner: RefCell<Option<I>>,
29 }
30
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::Result31 pub fn new_format<'a, I, F>(iter: I, separator: &'a str, f: F) -> FormatWith<'a, I, F>
32 where I: Iterator,
33 F: FnMut(I::Item, &mut dyn FnMut(&dyn fmt::Display) -> fmt::Result) -> fmt::Result
34 {
35 FormatWith {
36 sep: separator,
37 inner: RefCell::new(Some((iter, f))),
38 }
39 }
40
new_format_default<'a, I>(iter: I, separator: &'a str) -> Format<'a, I> where I: Iterator,41 pub fn new_format_default<'a, I>(iter: I, separator: &'a str) -> Format<'a, I>
42 where I: Iterator,
43 {
44 Format {
45 sep: separator,
46 inner: RefCell::new(Some(iter)),
47 }
48 }
49
50 impl<'a, I, F> fmt::Display for FormatWith<'a, I, F>
51 where I: Iterator,
52 F: FnMut(I::Item, &mut dyn FnMut(&dyn fmt::Display) -> fmt::Result) -> fmt::Result
53 {
fmt(&self, f: &mut fmt::Formatter) -> fmt::Result54 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
55 let (mut iter, mut format) = match self.inner.borrow_mut().take() {
56 Some(t) => t,
57 None => panic!("FormatWith: was already formatted once"),
58 };
59
60 if let Some(fst) = iter.next() {
61 format(fst, &mut |disp: &dyn fmt::Display| disp.fmt(f))?;
62 for elt in iter {
63 if self.sep.len() > 0 {
64
65 f.write_str(self.sep)?;
66 }
67 format(elt, &mut |disp: &dyn fmt::Display| disp.fmt(f))?;
68 }
69 }
70 Ok(())
71 }
72 }
73
74 impl<'a, I> Format<'a, I>
75 where I: Iterator,
76 {
format<F>(&self, f: &mut fmt::Formatter, mut cb: F) -> fmt::Result where F: FnMut(&I::Item, &mut fmt::Formatter) -> fmt::Result,77 fn format<F>(&self, f: &mut fmt::Formatter, mut cb: F) -> fmt::Result
78 where F: FnMut(&I::Item, &mut fmt::Formatter) -> fmt::Result,
79 {
80 let mut iter = match self.inner.borrow_mut().take() {
81 Some(t) => t,
82 None => panic!("Format: was already formatted once"),
83 };
84
85 if let Some(fst) = iter.next() {
86 cb(&fst, f)?;
87 for elt in iter {
88 if self.sep.len() > 0 {
89 f.write_str(self.sep)?;
90 }
91 cb(&elt, f)?;
92 }
93 }
94 Ok(())
95 }
96 }
97
98 macro_rules! impl_format {
99 ($($fmt_trait:ident)*) => {
100 $(
101 impl<'a, I> fmt::$fmt_trait for Format<'a, I>
102 where I: Iterator,
103 I::Item: fmt::$fmt_trait,
104 {
105 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
106 self.format(f, fmt::$fmt_trait::fmt)
107 }
108 }
109 )*
110 }
111 }
112
113 impl_format!{Display Debug
114 UpperExp LowerExp UpperHex LowerHex Octal Binary Pointer}
115