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Write a bunch of docs for char

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Mostly adding examples, and reformatting for consistency.
This commit is contained in:
Steve Klabnik 2015-10-05 18:09:31 -04:00
parent c298efdb1f
commit 51097fcdac
1 changed files with 393 additions and 76 deletions
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469
src/librustc_unicode/char.rs
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@ -110,53 +110,122 @@ fn next(&mut self) -> Option<char> {
#[stable(feature = "rust1", since = "1.0.0")]
#[lang = "char"]
impl char {
/// Checks if a `char` parses as a numeric digit in the given radix.
/// Checks if a `char` is a digit in the given radix.
///
/// A 'radix' here is sometimes also called a 'base'. A radix of two
/// indicates a binary number, a radix of ten, decimal, and a radix of
/// sixteen, hexicdecimal, to give some common values. Arbitrary
/// radicum are supported.
///
/// Compared to `is_numeric()`, this function only recognizes the characters
/// `0-9`, `a-z` and `A-Z`.
///
/// # Return value
/// 'Digit' is defined to be only the following characters:
///
/// Returns `true` if `c` is a valid digit under `radix`, and `false`
/// otherwise.
/// * `0-9`
/// * `a-z`
/// * `A-Z`
///
/// For a more comprehensive understanding of 'digit', see [`is_numeric()`][is_numeric].
///
/// [is_numeric]: #method.is_numeric
///
/// # Panics
///
/// Panics if given a radix > 36.
/// Panics if given a radix larger than 36.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = '1';
/// let d = '1';
///
/// assert!(c.is_digit(10));
/// assert!(d.is_digit(10));
///
/// assert!('f'.is_digit(16));
/// let d = 'f';
///
/// assert!(d.is_digit(16));
/// assert!(!d.is_digit(10));
/// ```
///
/// Passing a large radix, causing a panic:
///
/// ```
/// use std::thread;
///
/// let result = thread::spawn(|| {
/// let d = '1';
///
/// // this panics
/// d.is_digit(37);
/// }).join();
///
/// assert!(result.is_err());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_digit(self, radix: u32) -> bool { C::is_digit(self, radix) }
/// Converts a character to the corresponding digit.
/// Converts a `char` to a digit in the given radix.
///
/// # Return value
/// A 'radix' here is sometimes also called a 'base'. A radix of two
/// indicates a binary number, a radix of ten, decimal, and a radix of
/// sixteen, hexicdecimal, to give some common values. Arbitrary
/// radicum are supported.
///
/// If `c` is between '0' and '9', the corresponding value between 0 and
/// 9. If `c` is 'a' or 'A', 10. If `c` is 'b' or 'B', 11, etc. Returns
/// none if the character does not refer to a digit in the given radix.
/// 'Digit' is defined to be only the following characters:
///
/// * `0-9`
/// * `a-z`
/// * `A-Z`
///
/// # Failure
///
/// Returns `None` if the `char` does not refer to a digit in the given radix.
///
/// # Panics
///
/// Panics if given a radix outside the range [0..36].
/// Panics if given a radix larger than 36.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = '1';
/// let d = '1';
///
/// assert_eq!(c.to_digit(10), Some(1));
/// assert_eq!(d.to_digit(10), Some(1));
///
/// assert_eq!('f'.to_digit(16), Some(15));
/// let d = 'f';
///
/// assert_eq!(d.to_digit(16), Some(15));
/// ```
///
/// Passing a non-digit results in failure:
///
/// ```
/// let d = 'f';
///
/// assert_eq!(d.to_digit(10), None);
///
/// let d = 'z';
///
/// assert_eq!(d.to_digit(16), None);
/// ```
///
/// Passing a large radix, causing a panic:
///
/// ```
/// use std::thread;
///
/// let result = thread::spawn(|| {
/// let d = '1';
///
/// d.to_digit(37);
/// }).join();
///
/// assert!(result.is_err());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
@ -195,21 +264,29 @@ pub fn to_digit(self, radix: u32) -> Option<u32> { C::to_digit(self, radix) }
#[inline]
pub fn escape_unicode(self) -> EscapeUnicode { C::escape_unicode(self) }
/// Returns an iterator that yields the 'default' ASCII and
/// C++11-like literal escape of a character, as `char`s.
/// Returns an iterator that yields the literal escape code of a `char`.
///
/// The default is chosen with a bias toward producing literals that are
/// legal in a variety of languages, including C++11 and similar C-family
/// languages. The exact rules are:
///
/// * Tab, CR and LF are escaped as '\t', '\r' and '\n' respectively.
/// * Single-quote, double-quote and backslash chars are backslash-
/// escaped.
/// * Any other chars in the range [0x20,0x7e] are not escaped.
/// * Any other chars are given hex Unicode escapes; see `escape_unicode`.
/// * Tab is escaped as `\t`.
/// * Carriage return is escaped as `\r`.
/// * Line feed is escaped as `\n`.
/// * Single quote is escaped as `\'`.
/// * Double quote is escaped as `\"`.
/// * Backslash is escaped as `\\`.
/// * Any character in the 'printable ASCII' range `0x20` .. `0x7e`
/// inclusive is not escaped.
/// * All other characters are given hexadecimal Unicode escapes; see
/// [`escape_unicode`][escape_unicode].
///
/// [escape_unicode]: #method.escape_unicode
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// for i in '"'.escape_default() {
/// println!("{}", i);
@ -234,29 +311,70 @@ pub fn escape_unicode(self) -> EscapeUnicode { C::escape_unicode(self) }
#[inline]
pub fn escape_default(self) -> EscapeDefault { C::escape_default(self) }
/// Returns the number of bytes this character would need if encoded in
/// UTF-8.
/// Returns the number of bytes this `char` would need if encoded in UTF-8.
///
/// That number of bytes is always between 1 and 4, inclusive.
///
/// # Examples
///
/// ```
/// let n = 'ß'.len_utf8();
/// Basic usage:
///
/// assert_eq!(n, 2);
/// ```
/// let len = 'A'.len_utf8();
/// assert_eq!(len, 1);
///
/// let len = 'ß'.len_utf8();
/// assert_eq!(len, 2);
///
/// let len = 'ℝ'.len_utf8();
/// assert_eq!(len, 3);
///
/// let len = '💣'.len_utf8();
/// assert_eq!(len, 4);
/// ```
///
/// The `&str` type guarantees that its contents are UTF-8, and so we can compare the length it
/// would take if each code point was represented as a `char` vs in the `&str` itself:
///
/// ```
/// // as chars
/// let eastern = '東';
/// let capitol = '京';
///
/// // both can be represented as three bytes
/// assert_eq!(3, eastern.len_utf8());
/// assert_eq!(3, capitol.len_utf8());
///
/// // as a &str, these two are encoded in UTF-8
/// let tokyo = "東京";
///
/// let len = eastern.len_utf8() + capitol.len_utf8();
///
/// // we can see that they take six bytes total...
/// assert_eq!(6, tokyo.len());
///
/// // ... just like the &str
/// assert_eq!(len, tokyo.len());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn len_utf8(self) -> usize { C::len_utf8(self) }
/// Returns the number of 16-bit code units this character would need if
/// Returns the number of 16-bit code units this `char` would need if
/// encoded in UTF-16.
///
/// See the documentation for [`len_utf8()`][len_utf8] for more explanation
/// of this concept. This function is a mirror, but for UTF-16 instead of
/// UTF-8.
///
/// # Examples
///
/// ```
/// let n = 'ß'.len_utf16();
///
/// assert_eq!(n, 1);
///
/// let len = '💣'.len_utf16();
/// assert_eq!(len, 2);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
@ -342,8 +460,24 @@ pub fn encode_utf16(self, dst: &mut [u16]) -> Option<usize> {
C::encode_utf16(self, dst)
}
/// Returns whether the specified character is considered a Unicode
/// alphabetic code point.
/// Returns true if this `char` is an alphabetic code point, and false if not.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = 'a';
///
/// assert!(c.is_alphabetic());
///
/// let c = '京';
/// assert!(c.is_alphabetic());
///
/// let c = '💝';
/// // love is many things, but it is not alphabetic
/// assert!(!c.is_alphabetic());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_alphabetic(self) -> bool {
@ -354,20 +488,20 @@ pub fn is_alphabetic(self) -> bool {
}
}
/// Returns whether the specified character satisfies the 'XID_Start'
/// Unicode property.
/// Returns true if this `char` satisfies the 'XID_Start' Unicode property, and false
/// otherwise.
///
/// 'XID_Start' is a Unicode Derived Property specified in
/// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications),
/// mostly similar to ID_Start but modified for closure under NFKx.
/// mostly similar to `ID_Start` but modified for closure under `NFKx`.
#[unstable(feature = "unicode",
reason = "mainly needed for compiler internals",
issue = "0")]
#[inline]
pub fn is_xid_start(self) -> bool { derived_property::XID_Start(self) }
/// Returns whether the specified `char` satisfies the 'XID_Continue'
/// Unicode property.
/// Returns true if this `char` satisfies the 'XID_Continue' Unicode property, and false
/// otherwise.
///
/// 'XID_Continue' is a Unicode Derived Property specified in
/// [UAX #31](http://unicode.org/reports/tr31/#NFKC_Modifications),
@ -378,10 +512,32 @@ pub fn is_xid_start(self) -> bool { derived_property::XID_Start(self) }
#[inline]
pub fn is_xid_continue(self) -> bool { derived_property::XID_Continue(self) }
/// Indicates whether a character is in lowercase.
/// Returns true if this `char` is lowercase, and false otherwise.
///
/// This is defined according to the terms of the Unicode Derived Core
/// 'Lowercase' is defined according to the terms of the Unicode Derived Core
/// Property `Lowercase`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = 'a';
/// assert!(c.is_lowercase());
///
/// let c = 'δ';
/// assert!(c.is_lowercase());
///
/// let c = 'A';
/// assert!(!c.is_lowercase());
///
/// let c = 'Δ';
/// assert!(!c.is_lowercase());
///
/// // The various Chinese scripts do not have case, and so:
/// let c = '中';
/// assert!(!c.is_lowercase());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_lowercase(self) -> bool {
@ -392,10 +548,32 @@ pub fn is_lowercase(self) -> bool {
}
}
/// Indicates whether a character is in uppercase.
/// Returns true if this `char` is uppercase, and false otherwise.
///
/// This is defined according to the terms of the Unicode Derived Core
/// 'Uppercase' is defined according to the terms of the Unicode Derived Core
/// Property `Uppercase`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = 'a';
/// assert!(!c.is_uppercase());
///
/// let c = 'δ';
/// assert!(!c.is_uppercase());
///
/// let c = 'A';
/// assert!(c.is_uppercase());
///
/// let c = 'Δ';
/// assert!(c.is_uppercase());
///
/// // The various Chinese scripts do not have case, and so:
/// let c = '中';
/// assert!(!c.is_uppercase());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_uppercase(self) -> bool {
@ -406,9 +584,26 @@ pub fn is_uppercase(self) -> bool {
}
}
/// Indicates whether a character is whitespace.
/// Returns true if this `char` is whitespace, and false otherwise.
///
/// Whitespace is defined in terms of the Unicode Property `White_Space`.
/// 'Whitespace' is defined according to the terms of the Unicode Derived Core
/// Property `White_Space`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = ' ';
/// assert!(c.is_whitespace());
///
/// // a non-breaking space
/// let c = '\u{A0}';
/// assert!(c.is_whitespace());
///
/// let c = '越';
/// assert!(!c.is_whitespace());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_whitespace(self) -> bool {
@ -419,25 +614,101 @@ pub fn is_whitespace(self) -> bool {
}
}
/// Indicates whether a character is alphanumeric.
/// Returns true if this `char` is alphanumeric, and false otherwise.
///
/// Alphanumericness is defined in terms of the Unicode General Categories
/// 'Alphanumeric'-ness is defined in terms of the Unicode General Categories
/// 'Nd', 'Nl', 'No' and the Derived Core Property 'Alphabetic'.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = '٣';
/// assert!(c.is_alphanumeric());
///
/// let c = '7';
/// assert!(c.is_alphanumeric());
///
/// let c = '৬';
/// assert!(c.is_alphanumeric());
///
/// let c = 'K';
/// assert!(c.is_alphanumeric());
///
/// let c = 'و';
/// assert!(c.is_alphanumeric());
///
/// let c = '藏';
/// assert!(c.is_alphanumeric());
///
/// let c = '¾';
/// assert!(!c.is_alphanumeric());
///
/// let c = '①';
/// assert!(!c.is_alphanumeric());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_alphanumeric(self) -> bool {
self.is_alphabetic() || self.is_numeric()
}
/// Indicates whether a character is a control code point.
/// Returns true if this `char` is a control code point, and false otherwise.
///
/// Control code points are defined in terms of the Unicode General
/// 'Control code point' is defined in terms of the Unicode General
/// Category `Cc`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// // U+009C, STRING TERMINATOR
/// let c = 'œ';
/// assert!(c.is_control());
///
/// let c = 'q';
/// assert!(!c.is_control());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_control(self) -> bool { general_category::Cc(self) }
/// Indicates whether the character is numeric (Nd, Nl, or No).
/// Returns true if this `char` is numeric, and false otherwise.
///
/// 'Numeric'-ness is defined in terms of the Unicode General Categories
/// 'Nd', 'Nl', 'No'.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let c = '٣';
/// assert!(c.is_numeric());
///
/// let c = '7';
/// assert!(c.is_numeric());
///
/// let c = '৬';
/// assert!(c.is_numeric());
///
/// let c = 'K';
/// assert!(!c.is_numeric());
///
/// let c = 'و';
/// assert!(!c.is_numeric());
///
/// let c = '藏';
/// assert!(!c.is_numeric());
///
/// let c = '¾';
/// assert!(!c.is_numeric());
///
/// let c = '①';
/// assert!(!c.is_numeric());
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn is_numeric(self) -> bool {
@ -448,21 +719,36 @@ pub fn is_numeric(self) -> bool {
}
}
/// Converts a character to its lowercase equivalent.
/// Returns an iterator that yields the lowercase equivalent of a `char`.
///
/// This performs complex unconditional mappings with no tailoring.
/// See `to_uppercase()` for references and more information.
/// If no conversion is possible then an iterator with just the input character is returned.
///
/// # Return value
/// This performs complex unconditional mappings with no tailoring: it maps
/// one Unicode character to its lowercase equivalent according to the
/// [Unicode database] and the additional complex mappings
/// [`SpecialCasing.txt`]. Conditional mappings (based on context or
/// language) are not considered here.
///
/// Returns an iterator which yields the characters corresponding to the
/// lowercase equivalent of the character. If no conversion is possible then
/// an iterator with just the input character is returned.
/// For a full reference, see [here][reference].
///
/// [Unicode database]: ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
///
/// [`SpecialCasing.txt`]: ftp://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt
///
/// [reference]: http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// assert_eq!(Some('c'), 'C'.to_lowercase().next());
/// let c = 'c';
///
/// assert_eq!(c.to_uppercase().next(), Some('C'));
///
/// // Japanese scripts do not have case, and so:
/// let c = '山';
/// assert_eq!(c.to_uppercase().next(), Some('山'));
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
@ -470,33 +756,63 @@ pub fn to_lowercase(self) -> ToLowercase {
ToLowercase(CaseMappingIter::new(conversions::to_lower(self)))
}
/// Converts a character to its uppercase equivalent.
/// Returns an iterator that yields the uppercase equivalent of a `char`.
///
/// This performs complex unconditional mappings with no tailoring:
/// it maps one Unicode character to its uppercase equivalent
/// according to the Unicode database [1]
/// and the additional complex mappings [`SpecialCasing.txt`].
/// Conditional mappings (based on context or language) are not considered here.
/// If no conversion is possible then an iterator with just the input character is returned.
///
/// A full reference can be found here [2].
/// This performs complex unconditional mappings with no tailoring: it maps
/// one Unicode character to its uppercase equivalent according to the
/// [Unicode database] and the additional complex mappings
/// [`SpecialCasing.txt`]. Conditional mappings (based on context or
/// language) are not considered here.
///
/// # Return value
/// For a full reference, see [here][reference].
///
/// Returns an iterator which yields the characters corresponding to the
/// uppercase equivalent of the character. If no conversion is possible then
/// an iterator with just the input character is returned.
///
/// [1]: ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
/// [Unicode database]: ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
///
/// [`SpecialCasing.txt`]: ftp://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt
///
/// [2]: http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992
/// [reference]: http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// assert_eq!(Some('C'), 'c'.to_uppercase().next());
/// let c = 'c';
/// assert_eq!(c.to_uppercase().next(), Some('C'));
///
/// // Japanese does not have case, and so:
/// let c = '山';
/// assert_eq!(c.to_uppercase().next(), Some('山'));
/// ```
///
/// In Turkish, the equivalent of 'i' in Latin has five forms instead of two:
///
/// * 'Dotless': I / ı, sometimes written ï
/// * 'Dotted': İ / i
///
/// Note that the lowercase dotted 'i' is the same as the Latin. Therefore:
///
/// ```
/// let i = 'i';
///
/// let upper_i = i.to_uppercase().next();
/// ```
///
/// The value of `upper_i` here relies on the language of the text: if we're
/// in `en-US`, it should be `Some('I')`, but if we're in `tr_TR`, it should
/// be `Some('İ')`. `to_uppercase()` does not take this into account, and so:
///
/// ```
/// let i = 'i';
///
/// let upper_i = i.to_uppercase().next();
///
/// assert_eq!(Some('I'), upper_i);
/// ```
///
/// holds across languages.
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn to_uppercase(self) -> ToUppercase {
@ -504,7 +820,7 @@ pub fn to_uppercase(self) -> ToUppercase {
}
}
/// An iterator that decodes UTF-16 encoded codepoints from an iterator of `u16`s.
/// An iterator that decodes UTF-16 encoded code points from an iterator of `u16`s.
#[unstable(feature = "decode_utf16", reason = "recently exposed", issue = "27830")]
#[derive(Clone)]
pub struct DecodeUtf16<I> where I: Iterator<Item=u16> {
@ -512,7 +828,7 @@ pub struct DecodeUtf16<I> where I: Iterator<Item=u16> {
buf: Option<u16>,
}
/// Create an iterator over the UTF-16 encoded codepoints in `iterable`,
/// Create an iterator over the UTF-16 encoded code points in `iterable`,
/// returning unpaired surrogates as `Err`s.
///
/// # Examples
@ -612,7 +928,8 @@ fn size_hint(&self) -> (usize, Option<usize>) {
}
}
/// U+FFFD REPLACEMENT CHARACTER (<28>) is used in Unicode to represent a decoding error.
/// It can occur, for example, when giving ill-formed UTF-8 bytes to `String::from_utf8_lossy`.
/// `U+FFFD REPLACEMENT CHARACTER` (<28>) is used in Unicode to represent a decoding error.
/// It can occur, for example, when giving ill-formed UTF-8 bytes to
/// [`String::from_utf8_lossy`](../string/struct.String.html#method.from_utf8_lossy).
#[unstable(feature = "decode_utf16", reason = "recently added", issue = "27830")]
pub const REPLACEMENT_CHARACTER: char = '\u{FFFD}';