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#![doc(html_root_url = "https://docs.rs/thousands/0.1.3")] //! Provides a trait, [`Separable`], for formatting numbers with //! separators between the digits. Typically this will be used to add //! commas or spaces every three digits from the right, but can be //! configured via a [`SeparatorPolicy`]. //! //! # Examples //! //! The simplest way to use the library is with trait [`Separable`]’s method //! [`separate_with_commas`] method, which does what it sounds like: //! //! ``` //! use thousands::Separable; //! //! assert_eq!( 12345 .separate_with_commas(), "12,345" ); //! assert_eq!( (-12345) .separate_with_commas(), "-12,345" ); //! assert_eq!( 9876.5.separate_with_commas(), "9,876.5" ); //! ``` //! //! There are also methods [`separate_with_spaces`] and //! [`separate_with_dots`], in case you prefer those separators. //! //! However, it's also possible to pass a policy for different behavior: //! //! ``` //! use thousands::{Separable, SeparatorPolicy, digits}; //! //! let policy = SeparatorPolicy { //! separator: ',', //! groups: &[3, 2], //! digits: digits::ASCII_DECIMAL, //! }; //! //! assert_eq!( 1234567890.separate_by_policy(policy), "1,23,45,67,890" ); //! ``` //! //! # Usage //! //! It’s [on crates.io](https://crates.io/crates/thousands), so you can add //! //! ```toml //! [dependencies] //! thousands = "0.1.3" //! ``` //! //! to your `Cargo.toml`. //! //! This crate supports Rust version 1.17 and newer. //! //! [`Separable`]: trait.Separable.html //! [`SeparatorPolicy`]: struct.SeparatorPolicy.html //! [`separate_with_commas`]: trait.Separable.html#method.separate_with_commas //! [`separate_with_spaces`]: trait.Separable.html#method.separate_with_spaces //! [`separate_with_dots`]: trait.Separable.html#method.separate_with_dots use std::fmt::Display; /// Provides methods for formatting numbers with separators between the digits. pub trait Separable { /// Inserts a comma every three digits from the right. /// /// This is equivalent to `self.separate_by_policy(policies::COMMA_SEPARATOR)`. /// /// # Examples /// /// ``` /// # use thousands::*; /// assert_eq!( 12345.separate_with_commas(), "12,345" ); /// ``` fn separate_with_commas(&self) -> String { self.separate_by_policy(policies::COMMA_SEPARATOR) } /// Inserts a space every three digits from the right. /// /// This is equivalent to `self.separate_by_policy(policies::SPACE_SEPARATOR)`. /// /// # Examples /// /// ``` /// # use thousands::*; /// assert_eq!( 12345.separate_with_spaces(), "12 345" ); /// ``` fn separate_with_spaces(&self) -> String { self.separate_by_policy(policies::SPACE_SEPARATOR) } /// Inserts a period every three digits from the right. /// /// This is equivalent to `self.separate_by_policy(policies::DOT_SEPARATOR)`. /// /// # Examples /// /// ``` /// # use thousands::*; /// assert_eq!( 12345.separate_with_dots(), "12.345" ); /// ``` fn separate_with_dots(&self) -> String { self.separate_by_policy(policies::DOT_SEPARATOR) } /// Inserts an underscore every three digits from the right. /// /// This is equivalent to `self.separate_by_policy(policies::UNDERSCORE_SEPARATOR)`. /// /// # Examples /// /// ``` /// # use thousands::*; /// assert_eq!( 12345.separate_with_underscores(), "12_345" ); /// ``` fn separate_with_underscores(&self) -> String { self.separate_by_policy(policies::UNDERSCORE_SEPARATOR) } /// Adds separators according to the given [`SeparatorPolicy`]. /// /// # Examples /// /// ``` /// use thousands::{Separable, SeparatorPolicy, digits}; /// /// let policy = SeparatorPolicy { /// separator: ':', /// groups: &[1, 2, 3, 4], /// digits: digits::ASCII_DECIMAL, /// }; /// /// assert_eq!( 1234567654321u64.separate_by_policy(policy), /// "123:4567:654:32:1" ); /// ``` /// /// [`SeparatorPolicy`]: struct.SeparatorPolicy.html fn separate_by_policy(&self, policy: SeparatorPolicy) -> String; } impl<T: Display> Separable for T { fn separate_by_policy(&self, policy: SeparatorPolicy) -> String { let original = self.to_string(); let (before, number, after) = find_span(&original, |c| policy.digits.contains(&c)); let formatted = insert_separator_rev(number, policy.separator, policy.groups); let mut result = String::with_capacity(before.len() + formatted.len() + after.len()); result.push_str(before); result.extend(formatted.chars().rev()); result.push_str(after); result } } fn insert_separator_rev(number: &str, sep: char, mut groups: &[u8]) -> String { // Does guessing the size like on the next line make sense? let mut buffer = String::with_capacity(2 * number.len()); let mut counter = 0; for c in number.chars().rev() { if Some(&counter) == groups.get(0) { buffer.push(sep); counter = 0; if groups.len() > 1 { groups = &groups[1 ..]; } } counter += 1; buffer.push(c); } buffer } fn find_span<F>(s: &str, is_digit: F) -> (&str, &str, &str) where F: Fn(char) -> bool { let mut chars = s.chars().enumerate().skip_while(|&(_, c)| !is_digit(c)); let start = if let Some((i, _)) = chars.next() { i } else { return (s, "", ""); }; let stop = if let Some((i, _)) = chars.skip_while(|&(_, c)| is_digit(c)).next() { i } else { s.len() }; (&s[.. start], &s[start .. stop], &s[stop ..]) } /// A policy for inserting separators into numbers. /// /// The configurable aspects are: /// /// - The separator character to insert. /// /// - How to group the separators. /// /// - What characters are considered digits (for skipping non-digits such as /// a minus sign). #[derive(Debug, Clone, Copy)] pub struct SeparatorPolicy<'a> { /// The separator to insert. pub separator: char, /// The grouping. The numbers in this array give the size of the groups, from /// right to left, with the last number in the array giving the size of all /// subsequent groups. /// /// So to group by threes, as is typical in many places, /// this array should be `&[3]`. However, to get a grouping like `1,23,45,678`, /// where the last group has size three and the others size two, you would use /// `&[3, 2]`. pub groups: &'a [u8], /// The characters that are considered digits. If there are multiple groups of /// digits separated by non-digits, we only add separators to the first group. /// This means, for example, that the number `-12345.67` will only have separators /// inserted into the `12345` portion. pub digits: &'a [char], } /// Collections of digits. /// /// These are used for constructing [SeparatorPolicy](struct.SeparatorPolicy.html)s. pub mod digits { /// The decimal digits, in ASCII. pub const ASCII_DECIMAL: &[char] = &[ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', ]; /// The hexadecimal digits, in ASCII. pub const ASCII_HEXADECIMAL: &[char] = &[ '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f', 'A', 'B', 'C', 'D', 'E', 'F', ]; } /// Predefined policies. pub mod policies { use super::*; use super::digits::*; /// Policy for placing a comma every three decimal digits. pub const COMMA_SEPARATOR: SeparatorPolicy = SeparatorPolicy { separator: ',', groups: &[3], digits: ASCII_DECIMAL, }; /// Policy for placing a space every three decimal digits. pub const SPACE_SEPARATOR: SeparatorPolicy = SeparatorPolicy { separator: ' ', groups: &[3], digits: ASCII_DECIMAL, }; /// Policy for placing a period every three decimal digits. pub const DOT_SEPARATOR: SeparatorPolicy = SeparatorPolicy { separator: '.', groups: &[3], digits: ASCII_DECIMAL, }; /// Policy for placing an underscore every three decimal digits. pub const UNDERSCORE_SEPARATOR: SeparatorPolicy = SeparatorPolicy { separator: '_', groups: &[3], digits: ASCII_DECIMAL, }; /// Policy for placing a space every four hexadecimal digits. pub const HEX_FOUR: SeparatorPolicy = SeparatorPolicy { separator: ' ', groups: &[4], digits: ASCII_HEXADECIMAL, }; } #[cfg(test)] mod test { use super::*; #[test] fn integer_thousands_commas() { assert_eq!( 12345.separate_with_commas(), "12,345" ); } #[test] fn three_two_two_two() { let policy = SeparatorPolicy { separator: ',', groups: &[3, 2], digits: &digits::ASCII_DECIMAL, }; assert_eq!( 1234567890.separate_by_policy(policy), "1,23,45,67,890" ); } #[test] fn minus_sign_and_decimal_point() { assert_eq!( (-1234.5).separate_with_commas(), "-1,234.5" ); } #[test] fn hex_four() { assert_eq!( "deadbeef".separate_by_policy(policies::HEX_FOUR), "dead beef" ); } }