diff --git a/src/libcollections/str.rs b/src/libcollections/str.rs
index 25a3441fd5bb6..7c64dea3dc338 100644
--- a/src/libcollections/str.rs
+++ b/src/libcollections/str.rs
@@ -500,7 +500,7 @@ impl str {
///
/// # Unsafety
///
- /// Caller must check both UTF-8 character boundaries and the boundaries
+ /// Caller must check both UTF-8 sequence boundaries and the boundaries
/// of the entire slice as
/// well.
///
@@ -526,15 +526,16 @@ impl str {
core_str::StrExt::slice_mut_unchecked(self, begin, end)
}
- /// Returns a slice of the string from the character range [`begin`..`end`).
+ /// Returns a slice of the string from the range [`begin`..`end`) where indices
+ /// are counted in code points.
///
/// That is, start at the `begin`-th code point of the string and continue
/// to the `end`-th code point. This does not detect or handle edge cases
- /// such as leaving a combining character as the first code point of the
+ /// such as leaving a combining character as the first `char` of the
/// string.
///
/// Due to the design of UTF-8, this operation is `O(end)`. Use slicing
- /// syntax if you want to use byte indices rather than codepoint indices.
+ /// syntax if you want to use `O(1)` byte indices instead.
///
/// # Panics
///
@@ -556,18 +557,18 @@ impl str {
core_str::StrExt::slice_chars(self, begin, end)
}
- /// Given a byte position, return the next char and its index.
+ /// Given a byte position, return the next code point and its index.
///
- /// This can be used to iterate over the Unicode characters of a string.
+ /// This can be used to iterate over the Unicode code points of a string.
///
/// # Panics
///
/// If `i` is greater than or equal to the length of the string.
- /// If `i` is not the index of the beginning of a valid UTF-8 character.
+ /// If `i` is not the index of the beginning of a valid UTF-8 sequence.
///
/// # Examples
///
- /// This example manually iterates through the characters of a string;
+ /// This example manually iterates through the code points of a string;
/// this should normally be
/// done by `.chars()` or `.char_indices()`.
///
@@ -575,7 +576,7 @@ impl str {
/// # #![feature(str_char, core)]
/// use std::str::CharRange;
///
- /// let s = "中华Việt Nam";
+ /// let s = "中华Việt Nam";
/// let mut i = 0;
/// while i < s.len() {
/// let CharRange {ch, next} = s.char_range_at(i);
@@ -591,12 +592,14 @@ impl str {
/// 3: 华
/// 6: V
/// 7: i
- /// 8: ệ
- /// 11: t
- /// 12:
- /// 13: N
- /// 14: a
- /// 15: m
+ /// 8: e
+ /// 9: ̣
+ /// 11: ̂
+ /// 13: t
+ /// 14:
+ /// 15: N
+ /// 16: a
+ /// 17: m
/// ```
#[unstable(feature = "str_char",
reason = "often replaced by char_indices, this method may \
@@ -608,18 +611,21 @@ impl str {
/// Given a byte position, return the previous `char` and its position.
///
- /// This function can be used to iterate over a Unicode string in reverse.
+ /// This function can be used to iterate over a Unicode code points in reverse.
+ ///
+ /// Note that Unicode has many features, such as combining marks, ligatures,
+ /// and direction marks, that need to be taken into account to correctly reverse a string.
///
/// Returns 0 for next index if called on start index 0.
///
/// # Panics
///
/// If `i` is greater than the length of the string.
- /// If `i` is not an index following a valid UTF-8 character.
+ /// If `i` is not an index following a valid UTF-8 sequence.
///
/// # Examples
///
- /// This example manually iterates through the characters of a string;
+ /// This example manually iterates through the code points of a string;
/// this should normally be
/// done by `.chars().rev()` or `.char_indices()`.
///
@@ -627,7 +633,7 @@ impl str {
/// # #![feature(str_char, core)]
/// use std::str::CharRange;
///
- /// let s = "中华Việt Nam";
+ /// let s = "中华Việt Nam";
/// let mut i = s.len();
/// while i > 0 {
/// let CharRange {ch, next} = s.char_range_at_reverse(i);
@@ -639,12 +645,14 @@ impl str {
/// This outputs:
///
/// ```text
- /// 16: m
- /// 15: a
- /// 14: N
- /// 13:
- /// 12: t
- /// 11: ệ
+ /// 18: m
+ /// 17: a
+ /// 16: N
+ /// 15:
+ /// 14: t
+ /// 13: ̂
+ /// 11: ̣
+ /// 9: e
/// 8: i
/// 7: V
/// 6: 华
@@ -663,7 +671,7 @@ impl str {
/// # Panics
///
/// If `i` is greater than or equal to the length of the string.
- /// If `i` is not the index of the beginning of a valid UTF-8 character.
+ /// If `i` is not the index of the beginning of a valid UTF-8 sequence.
///
/// # Examples
///
@@ -672,6 +680,7 @@ impl str {
/// let s = "abπc";
/// assert_eq!(s.char_at(1), 'b');
/// assert_eq!(s.char_at(2), 'π');
+ /// assert_eq!(s.char_at(4), 'c');
/// ```
#[unstable(feature = "str_char",
reason = "frequently replaced by the chars() iterator, this \
@@ -689,7 +698,7 @@ impl str {
/// # Panics
///
/// If `i` is greater than the length of the string.
- /// If `i` is not an index following a valid UTF-8 character.
+ /// If `i` is not an index following a valid UTF-8 sequence.
///
/// # Examples
///
@@ -698,6 +707,7 @@ impl str {
/// let s = "abπc";
/// assert_eq!(s.char_at_reverse(1), 'a');
/// assert_eq!(s.char_at_reverse(2), 'b');
+ /// assert_eq!(s.char_at_reverse(3), 'π');
/// ```
#[unstable(feature = "str_char",
reason = "see char_at for more details, but reverse semantics \
@@ -707,28 +717,30 @@ impl str {
core_str::StrExt::char_at_reverse(self, i)
}
- /// Retrieves the first character from a `&str` and returns it.
+ /// Retrieves the first code point from a `&str` and returns it.
+ ///
+ /// Note that a single Unicode character (grapheme cluster)
+ /// can be composed of multiple `char`s.
///
/// This does not allocate a new string; instead, it returns a slice that
- /// points one character
- /// beyond the character that was shifted.
+ /// points one code point beyond the code point that was shifted.
///
- /// If the slice does not contain any characters, None is returned instead.
+ /// `None` is returned if the slice is empty.
///
/// # Examples
///
/// ```
/// # #![feature(str_char)]
- /// let s = "Löwe 老虎 Léopard";
+ /// let s = "Łódź"; // \u{141}o\u{301}dz\u{301}
/// let (c, s1) = s.slice_shift_char().unwrap();
///
- /// assert_eq!(c, 'L');
- /// assert_eq!(s1, "öwe 老虎 Léopard");
+ /// assert_eq!(c, 'Ł');
+ /// assert_eq!(s1, "ódź");
///
/// let (c, s2) = s1.slice_shift_char().unwrap();
///
- /// assert_eq!(c, 'ö');
- /// assert_eq!(s2, "we 老虎 Léopard");
+ /// assert_eq!(c, 'o');
+ /// assert_eq!(s2, "\u{301}dz\u{301}");
/// ```
#[unstable(feature = "str_char",
reason = "awaiting conventions about shifting and slices and \
@@ -741,14 +753,14 @@ impl str {
/// Divide one string slice into two at an index.
///
/// The index `mid` is a byte offset from the start of the string
- /// that must be on a character boundary.
+ /// that must be on a `char` boundary.
///
/// Return slices `&self[..mid]` and `&self[mid..]`.
///
/// # Panics
///
- /// Panics if `mid` is beyond the last character of the string,
- /// or if it is not on a character boundary.
+ /// Panics if `mid` is beyond the last code point of the string,
+ /// or if it is not on a `char` boundary.
///
/// # Examples
/// ```
@@ -773,27 +785,39 @@ impl str {
core_str::StrExt::split_at_mut(self, mid)
}
- /// An iterator over the codepoints of `self`.
+ /// An iterator over the code points of `self`.
+ ///
+ /// In Unicode relationship between code points and characters is complex.
+ /// A single character may be composed of multiple code points
+ /// (e.g. diacritical marks added to a letter), and a single code point
+ /// (e.g. Hangul syllable) may contain multiple characters.
+ ///
+ /// For iteration over human-readable characters a grapheme cluster iterator
+ /// may be more appropriate. See the [unicode-segmentation crate][1].
+ ///
+ /// [1]: https://crates.io/crates/unicode-segmentation
///
/// # Examples
///
/// ```
- /// let v: Vec<char> = "abc åäö".chars().collect();
+ /// let v: Vec<char> = "ASCII żółć 🇨🇭 한".chars().collect();
///
- /// assert_eq!(v, ['a', 'b', 'c', ' ', 'å', 'ä', 'ö']);
+ /// assert_eq!(v, ['A', 'S', 'C', 'I', 'I', ' ',
+ /// 'z', '\u{307}', 'o', '\u{301}', 'ł', 'c', '\u{301}', ' ',
+ /// '\u{1f1e8}', '\u{1f1ed}', ' ', '한']);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn chars(&self) -> Chars {
core_str::StrExt::chars(self)
}
- /// An iterator over the characters of `self` and their byte offsets.
+ /// An iterator over the `char`s of `self` and their byte offsets.
///
/// # Examples
///
/// ```
- /// let v: Vec<(usize, char)> = "abc".char_indices().collect();
- /// let b = vec![(0, 'a'), (1, 'b'), (2, 'c')];
+ /// let v: Vec<(usize, char)> = "A🇨🇭".char_indices().collect();
+ /// let b = vec![(0, 'A'), (1, '\u{1f1e8}'), (5, '\u{1f1ed}')];
///
/// assert_eq!(v, b);
/// ```
@@ -822,7 +846,7 @@ impl str {
/// # Examples
///
/// ```
- /// let some_words = " Mary had\ta little \n\t lamb";
+ /// let some_words = " Mary had\ta\u{2009}little \n\t lamb";
/// let v: Vec<&str> = some_words.split_whitespace().collect();
///
/// assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);
@@ -840,7 +864,7 @@ impl str {
/// ```
/// # #![feature(str_words)]
/// # #![allow(deprecated)]
- /// let some_words = " Mary had\ta little \n\t lamb";
+ /// let some_words = " Mary had\ta\u{2009}little \n\t lamb";
/// let v: Vec<&str> = some_words.words().collect();
///
/// assert_eq!(v, ["Mary", "had", "a", "little", "lamb"]);