Primitive Type char

A character type.

The char type represents a single character. More specifically, since 'character' isn't a well-defined concept in Unicode, char is a 'Unicode scalar value', which is similar to, but not the same as, a 'Unicode code point'.

This documentation describes a number of methods and trait implementations on the char type. For technical reasons, there is additional, separate documentation in the std::char module as well.

Representation

char is always four bytes in size. This is a different representation than a given character would have as part of a String. For example:

let v = vec!['h', 'e', 'l', 'l', 'o'];

// five elements times four bytes for each element
assert_eq!(20, v.len() * std::mem::size_of::<char>());

let s = String::from("hello");

// five elements times one byte per element
assert_eq!(5, s.len() * std::mem::size_of::<u8>());

As always, remember that a human intuition for 'character' may not map to Unicode's definitions. For example, despite looking similar, the 'é' character is one Unicode code point while 'é' is two Unicode code points:

let mut chars = "é".chars();
// U+00e9: 'latin small letter e with acute'
assert_eq!(Some('\u{00e9}'), chars.next());
assert_eq!(None, chars.next());

let mut chars = "é".chars();
// U+0065: 'latin small letter e'
assert_eq!(Some('\u{0065}'), chars.next());
// U+0301: 'combining acute accent'
assert_eq!(Some('\u{0301}'), chars.next());
assert_eq!(None, chars.next());

This means that the contents of the first string above will fit into a char while the contents of the second string will not. Trying to create a char literal with the contents of the second string gives an error:

error: character literal may only contain one codepoint: 'é'
let c = 'é';
        ^^^

Another implication of the 4-byte fixed size of a char is that per-char processing can end up using a lot more memory:

let s = String::from("love: ❤️");
let v: Vec<char> = s.chars().collect();

assert_eq!(12, std::mem::size_of_val(&s[..]));
assert_eq!(32, std::mem::size_of_val(&v[..]));

Methods

impl char

pub fn is_digit(self, radix: u32) -> bool

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, hexadecimal, to give some common values. Arbitrary radices are supported.

Compared to is_numeric(), this function only recognizes the characters 0-9, a-z and A-Z.

'Digit' is defined to be only the following characters:

• 0-9
• a-z
• A-Z

For a more comprehensive understanding of 'digit', see is_numeric.

Panics

Panics if given a radix larger than 36.

Examples

Basic usage:

assert!('1'.is_digit(10));
assert!('f'.is_digit(16));
assert!(!'f'.is_digit(10));

Passing a large radix, causing a panic:

use std::thread;

let result = thread::spawn(|| {
    // this panics
    '1'.is_digit(37);
}).join();

assert!(result.is_err());

pub fn to_digit(self, radix: u32) -> Option<u32>

Converts a char to 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, hexadecimal, to give some common values. Arbitrary radices are supported.

'Digit' is defined to be only the following characters:

• 0-9
• a-z
• A-Z

Errors

Returns None if the char does not refer to a digit in the given radix.

Panics

Panics if given a radix larger than 36.

Examples

Basic usage:

assert_eq!('1'.to_digit(10), Some(1));
assert_eq!('f'.to_digit(16), Some(15));

Passing a non-digit results in failure:

assert_eq!('f'.to_digit(10), None);
assert_eq!('z'.to_digit(16), None);

Passing a large radix, causing a panic:

use std::thread;

let result = thread::spawn(|| {
    '1'.to_digit(37);
}).join();

assert!(result.is_err());

Important traits for EscapeUnicode

impl Iterator for EscapeUnicode type Item = char;

pub fn escape_unicode(self) -> EscapeUnicode

Returns an iterator that yields the hexadecimal Unicode escape of a character as chars.

This will escape characters with the Rust syntax of the form \u{NNNNNN} where NNNNNN is a hexadecimal representation.

Examples

As an iterator:

for c in '❤'.escape_unicode() {
    print!("{}", c);
}
println!();

Using println! directly:

println!("{}", '❤'.escape_unicode());

Both are equivalent to:

println!("\\u{{2764}}");

Using to_string:

assert_eq!('❤'.escape_unicode().to_string(), "\\u{2764}");

Important traits for EscapeDebug

impl Iterator for EscapeDebug type Item = char;

pub fn escape_debug(self) -> EscapeDebug

Returns an iterator that yields the literal escape code of a character as chars.

This will escape the characters similar to the Debug implementations of str or char.

Examples

As an iterator:

for c in '\n'.escape_debug() {
    print!("{}", c);
}
println!();

Using println! directly:

println!("{}", '\n'.escape_debug());

Both are equivalent to:

println!("\\n");

Using to_string:

assert_eq!('\n'.escape_debug().to_string(), "\\n");

Important traits for EscapeDefault

impl Iterator for EscapeDefault type Item = char;

pub fn escape_default(self) -> EscapeDefault

Returns an iterator that yields the literal escape code of a character as chars.

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 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.

Examples

As an iterator:

for c in '"'.escape_default() {
    print!("{}", c);
}
println!();

Using println! directly:

println!("{}", '"'.escape_default());

Both are equivalent to:

println!("\\\"");

Using to_string:

assert_eq!('"'.escape_default().to_string(), "\\\"");

pub fn len_utf8(self) -> usize

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

Basic usage:

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 capital = '京';

// both can be represented as three bytes
assert_eq!(3, eastern.len_utf8());
assert_eq!(3, capital.len_utf8());

// as a &str, these two are encoded in UTF-8
let tokyo = "東京";

let len = eastern.len_utf8() + capital.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());

pub fn len_utf16(self) -> usize

Returns the number of 16-bit code units this char would need if encoded in UTF-16.

See the documentation for len_utf8 for more explanation of this concept. This function is a mirror, but for UTF-16 instead of UTF-8.

Examples

Basic usage:

let n = 'ß'.len_utf16();
assert_eq!(n, 1);

let len = '💣'.len_utf16();
assert_eq!(len, 2);

pub fn encode_utf8(self, dst: &mut [u8]) -> &mut str

Encodes this character as UTF-8 into the provided byte buffer, and then returns the subslice of the buffer that contains the encoded character.

Panics

Panics if the buffer is not large enough. A buffer of length four is large enough to encode any char.

Examples

In both of these examples, 'ß' takes two bytes to encode.

let mut b = [0; 2];

let result = 'ß'.encode_utf8(&mut b);

assert_eq!(result, "ß");

assert_eq!(result.len(), 2);

A buffer that's too small:

use std::thread;

let result = thread::spawn(|| {
    let mut b = [0; 1];

    // this panics
   'ß'.encode_utf8(&mut b);
}).join();

assert!(result.is_err());

Important traits for &'_ [u8]

impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]

pub fn encode_utf16(self, dst: &mut [u16]) -> &mut [u16]

Encodes this character as UTF-16 into the provided u16 buffer, and then returns the subslice of the buffer that contains the encoded character.

Panics

Panics if the buffer is not large enough. A buffer of length 2 is large enough to encode any char.

Examples

In both of these examples, '𝕊' takes two u16s to encode.

let mut b = [0; 2];

let result = '𝕊'.encode_utf16(&mut b);

assert_eq!(result.len(), 2);

A buffer that's too small:

use std::thread;

let result = thread::spawn(|| {
    let mut b = [0; 1];

    // this panics
    '𝕊'.encode_utf16(&mut b);
}).join();

assert!(result.is_err());

pub fn is_alphabetic(self) -> bool

Returns true if this char is an alphabetic code point, and false if not.

Examples

Basic usage:

assert!('a'.is_alphabetic());
assert!('京'.is_alphabetic());

let c = '💝';
// love is many things, but it is not alphabetic
assert!(!c.is_alphabetic());

pub fn is_xid_start(self) -> bool

🔬 This is a nightly-only experimental API. (unicode_internals #0)

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, mostly similar to ID_Start but modified for closure under NFKx.

pub fn is_xid_continue(self) -> bool

🔬 This is a nightly-only experimental API. (unicode_internals #0)

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, mostly similar to ID_Continue but modified for closure under NFKx.

pub fn is_lowercase(self) -> bool

Returns true if this char is lowercase.

'Lowercase' is defined according to the terms of the Unicode Derived Core Property Lowercase.

Examples

Basic usage:

assert!('a'.is_lowercase());
assert!('δ'.is_lowercase());
assert!(!'A'.is_lowercase());
assert!(!'Δ'.is_lowercase());

// The various Chinese scripts do not have case, and so:
assert!(!'中'.is_lowercase());

pub fn is_uppercase(self) -> bool

Returns true if this char is uppercase.

'Uppercase' is defined according to the terms of the Unicode Derived Core Property Uppercase.

Examples

Basic usage:

assert!(!'a'.is_uppercase());
assert!(!'δ'.is_uppercase());
assert!('A'.is_uppercase());
assert!('Δ'.is_uppercase());

// The various Chinese scripts do not have case, and so:
assert!(!'中'.is_uppercase());

pub fn is_whitespace(self) -> bool

Returns true if this char is whitespace.

'Whitespace' is defined according to the terms of the Unicode Derived Core Property White_Space.

Examples

Basic usage:

assert!(' '.is_whitespace());

// a non-breaking space
assert!('\u{A0}'.is_whitespace());

assert!(!'越'.is_whitespace());

pub fn is_alphanumeric(self) -> bool

Returns true if this char is alphanumeric.

'Alphanumeric'-ness is defined in terms of the Unicode General Categories Nd, Nl, No and the Derived Core Property Alphabetic.

Examples

Basic usage:

assert!('٣'.is_alphanumeric());
assert!('7'.is_alphanumeric());
assert!('৬'.is_alphanumeric());
assert!('¾'.is_alphanumeric());
assert!('①'.is_alphanumeric());
assert!('K'.is_alphanumeric());
assert!('و'.is_alphanumeric());
assert!('藏'.is_alphanumeric());

pub fn is_control(self) -> bool

Returns true if this char is a control code point.

'Control code point' is defined in terms of the Unicode General Category Cc.

Examples

Basic usage:

// U+009C, STRING TERMINATOR
assert!('œ'.is_control());
assert!(!'q'.is_control());

pub fn is_numeric(self) -> bool

Returns true if this char is numeric.

'Numeric'-ness is defined in terms of the Unicode General Categories Nd, Nl, No.

Examples

Basic usage:

assert!('٣'.is_numeric());
assert!('7'.is_numeric());
assert!('৬'.is_numeric());
assert!('¾'.is_numeric());
assert!('①'.is_numeric());
assert!(!'K'.is_numeric());
assert!(!'و'.is_numeric());
assert!(!'藏'.is_numeric());

Important traits for ToLowercase

impl Iterator for ToLowercase type Item = char;

pub fn to_lowercase(self) -> ToLowercase

Returns an iterator that yields the lowercase equivalent of a char as one or more chars.

If a character does not have a lowercase equivalent, the same character will be returned back by the iterator.

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.

For a full reference, see here.

Examples

As an iterator:

for c in 'İ'.to_lowercase() {
    print!("{}", c);
}
println!();

Using println! directly:

println!("{}", 'İ'.to_lowercase());

Both are equivalent to:

println!("i\u{307}");

Using to_string:

assert_eq!('C'.to_lowercase().to_string(), "c");

// Sometimes the result is more than one character:
assert_eq!('İ'.to_lowercase().to_string(), "i\u{307}");

// Characters that do not have both uppercase and lowercase
// convert into themselves.
assert_eq!('山'.to_lowercase().to_string(), "山");

Important traits for ToUppercase

impl Iterator for ToUppercase type Item = char;

pub fn to_uppercase(self) -> ToUppercase

Returns an iterator that yields the uppercase equivalent of a char as one or more chars.

If a character does not have an uppercase equivalent, the same character will be returned back by the iterator.

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.

For a full reference, see here.

Examples

As an iterator:

for c in 'ß'.to_uppercase() {
    print!("{}", c);
}
println!();

Using println! directly:

println!("{}", 'ß'.to_uppercase());

Both are equivalent to:

println!("SS");

Using to_string:

assert_eq!('c'.to_uppercase().to_string(), "C");

// Sometimes the result is more than one character:
assert_eq!('ß'.to_uppercase().to_string(), "SS");

// Characters that do not have both uppercase and lowercase
// convert into themselves.
assert_eq!('山'.to_uppercase().to_string(), "山");

Note on locale

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 upper_i = 'i'.to_uppercase().to_string();

The value of upper_i here relies on the language of the text: if we're in en-US, it should be "I", but if we're in tr_TR, it should be "İ". to_uppercase() does not take this into account, and so:

let upper_i = 'i'.to_uppercase().to_string();

assert_eq!(upper_i, "I");

holds across languages.

pub const fn is_ascii(&self) -> bool

Checks if the value is within the ASCII range.

Examples

let ascii = 'a';
let non_ascii = '❤';

assert!(ascii.is_ascii());
assert!(!non_ascii.is_ascii());

pub fn to_ascii_uppercase(&self) -> char

Makes a copy of the value in its ASCII upper case equivalent.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To uppercase the value in-place, use make_ascii_uppercase.

To uppercase ASCII characters in addition to non-ASCII characters, use to_uppercase.

Examples

let ascii = 'a';
let non_ascii = '❤';

assert_eq!('A', ascii.to_ascii_uppercase());
assert_eq!('❤', non_ascii.to_ascii_uppercase());

pub fn to_ascii_lowercase(&self) -> char

Makes a copy of the value in its ASCII lower case equivalent.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To lowercase the value in-place, use make_ascii_lowercase.

To lowercase ASCII characters in addition to non-ASCII characters, use to_lowercase.

Examples

let ascii = 'A';
let non_ascii = '❤';

assert_eq!('a', ascii.to_ascii_lowercase());
assert_eq!('❤', non_ascii.to_ascii_lowercase());

pub fn eq_ignore_ascii_case(&self, other: &char) -> bool

Checks that two values are an ASCII case-insensitive match.

Equivalent to to_ascii_lowercase(a) == to_ascii_lowercase(b).

Examples

let upper_a = 'A';
let lower_a = 'a';
let lower_z = 'z';

assert!(upper_a.eq_ignore_ascii_case(&lower_a));
assert!(upper_a.eq_ignore_ascii_case(&upper_a));
assert!(!upper_a.eq_ignore_ascii_case(&lower_z));

pub fn make_ascii_uppercase(&mut self)

Converts this type to its ASCII upper case equivalent in-place.

ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', but non-ASCII letters are unchanged.

To return a new uppercased value without modifying the existing one, use to_ascii_uppercase.

Examples

let mut ascii = 'a';

ascii.make_ascii_uppercase();

assert_eq!('A', ascii);

pub fn make_ascii_lowercase(&mut self)

Converts this type to its ASCII lower case equivalent in-place.

ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', but non-ASCII letters are unchanged.

To return a new lowercased value without modifying the existing one, use to_ascii_lowercase.

Examples

let mut ascii = 'A';

ascii.make_ascii_lowercase();

assert_eq!('a', ascii);

pub fn is_ascii_alphabetic(&self) -> bool

Checks if the value is an ASCII alphabetic character:

• U+0041 'A' ..= U+005A 'Z', or
• U+0061 'a' ..= U+007A 'z'.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(uppercase_a.is_ascii_alphabetic());
assert!(uppercase_g.is_ascii_alphabetic());
assert!(a.is_ascii_alphabetic());
assert!(g.is_ascii_alphabetic());
assert!(!zero.is_ascii_alphabetic());
assert!(!percent.is_ascii_alphabetic());
assert!(!space.is_ascii_alphabetic());
assert!(!lf.is_ascii_alphabetic());
assert!(!esc.is_ascii_alphabetic());

pub fn is_ascii_uppercase(&self) -> bool

Checks if the value is an ASCII uppercase character: U+0041 'A' ..= U+005A 'Z'.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(uppercase_a.is_ascii_uppercase());
assert!(uppercase_g.is_ascii_uppercase());
assert!(!a.is_ascii_uppercase());
assert!(!g.is_ascii_uppercase());
assert!(!zero.is_ascii_uppercase());
assert!(!percent.is_ascii_uppercase());
assert!(!space.is_ascii_uppercase());
assert!(!lf.is_ascii_uppercase());
assert!(!esc.is_ascii_uppercase());

pub fn is_ascii_lowercase(&self) -> bool

Checks if the value is an ASCII lowercase character: U+0061 'a' ..= U+007A 'z'.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(!uppercase_a.is_ascii_lowercase());
assert!(!uppercase_g.is_ascii_lowercase());
assert!(a.is_ascii_lowercase());
assert!(g.is_ascii_lowercase());
assert!(!zero.is_ascii_lowercase());
assert!(!percent.is_ascii_lowercase());
assert!(!space.is_ascii_lowercase());
assert!(!lf.is_ascii_lowercase());
assert!(!esc.is_ascii_lowercase());

pub fn is_ascii_alphanumeric(&self) -> bool

Checks if the value is an ASCII alphanumeric character:

• U+0041 'A' ..= U+005A 'Z', or
• U+0061 'a' ..= U+007A 'z', or
• U+0030 '0' ..= U+0039 '9'.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(uppercase_a.is_ascii_alphanumeric());
assert!(uppercase_g.is_ascii_alphanumeric());
assert!(a.is_ascii_alphanumeric());
assert!(g.is_ascii_alphanumeric());
assert!(zero.is_ascii_alphanumeric());
assert!(!percent.is_ascii_alphanumeric());
assert!(!space.is_ascii_alphanumeric());
assert!(!lf.is_ascii_alphanumeric());
assert!(!esc.is_ascii_alphanumeric());

pub fn is_ascii_digit(&self) -> bool

Checks if the value is an ASCII decimal digit: U+0030 '0' ..= U+0039 '9'.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(!uppercase_a.is_ascii_digit());
assert!(!uppercase_g.is_ascii_digit());
assert!(!a.is_ascii_digit());
assert!(!g.is_ascii_digit());
assert!(zero.is_ascii_digit());
assert!(!percent.is_ascii_digit());
assert!(!space.is_ascii_digit());
assert!(!lf.is_ascii_digit());
assert!(!esc.is_ascii_digit());

pub fn is_ascii_hexdigit(&self) -> bool

Checks if the value is an ASCII hexadecimal digit:

• U+0030 '0' ..= U+0039 '9', or
• U+0041 'A' ..= U+0046 'F', or
• U+0061 'a' ..= U+0066 'f'.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(uppercase_a.is_ascii_hexdigit());
assert!(!uppercase_g.is_ascii_hexdigit());
assert!(a.is_ascii_hexdigit());
assert!(!g.is_ascii_hexdigit());
assert!(zero.is_ascii_hexdigit());
assert!(!percent.is_ascii_hexdigit());
assert!(!space.is_ascii_hexdigit());
assert!(!lf.is_ascii_hexdigit());
assert!(!esc.is_ascii_hexdigit());

pub fn is_ascii_punctuation(&self) -> bool

Checks if the value is an ASCII punctuation character:

• U+0021 ..= U+002F ! " # $ % & ' ( ) * + , - . /, or
• U+003A ..= U+0040 : ; < = > ? @, or
• U+005B ..= U+0060 [ \ ] ^ _ ` , or
• U+007B ..= U+007E { | } ~

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(!uppercase_a.is_ascii_punctuation());
assert!(!uppercase_g.is_ascii_punctuation());
assert!(!a.is_ascii_punctuation());
assert!(!g.is_ascii_punctuation());
assert!(!zero.is_ascii_punctuation());
assert!(percent.is_ascii_punctuation());
assert!(!space.is_ascii_punctuation());
assert!(!lf.is_ascii_punctuation());
assert!(!esc.is_ascii_punctuation());

pub fn is_ascii_graphic(&self) -> bool

Checks if the value is an ASCII graphic character: U+0021 '!' ..= U+007E '~'.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(uppercase_a.is_ascii_graphic());
assert!(uppercase_g.is_ascii_graphic());
assert!(a.is_ascii_graphic());
assert!(g.is_ascii_graphic());
assert!(zero.is_ascii_graphic());
assert!(percent.is_ascii_graphic());
assert!(!space.is_ascii_graphic());
assert!(!lf.is_ascii_graphic());
assert!(!esc.is_ascii_graphic());

pub fn is_ascii_whitespace(&self) -> bool

Checks if the value is an ASCII whitespace character: U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED, U+000C FORM FEED, or U+000D CARRIAGE RETURN.

Rust uses the WhatWG Infra Standard's definition of ASCII whitespace. There are several other definitions in wide use. For instance, the POSIX locale includes U+000B VERTICAL TAB as well as all the above characters, but—from the very same specification—the default rule for "field splitting" in the Bourne shell considers only SPACE, HORIZONTAL TAB, and LINE FEED as whitespace.

If you are writing a program that will process an existing file format, check what that format's definition of whitespace is before using this function.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(!uppercase_a.is_ascii_whitespace());
assert!(!uppercase_g.is_ascii_whitespace());
assert!(!a.is_ascii_whitespace());
assert!(!g.is_ascii_whitespace());
assert!(!zero.is_ascii_whitespace());
assert!(!percent.is_ascii_whitespace());
assert!(space.is_ascii_whitespace());
assert!(lf.is_ascii_whitespace());
assert!(!esc.is_ascii_whitespace());

pub fn is_ascii_control(&self) -> bool

Checks if the value is an ASCII control character: U+0000 NUL ..= U+001F UNIT SEPARATOR, or U+007F DELETE. Note that most ASCII whitespace characters are control characters, but SPACE is not.

Examples

let uppercase_a = 'A';
let uppercase_g = 'G';
let a = 'a';
let g = 'g';
let zero = '0';
let percent = '%';
let space = ' ';
let lf = '\n';
let esc: char = 0x1b_u8.into();

assert!(!uppercase_a.is_ascii_control());
assert!(!uppercase_g.is_ascii_control());
assert!(!a.is_ascii_control());
assert!(!g.is_ascii_control());
assert!(!zero.is_ascii_control());
assert!(!percent.is_ascii_control());
assert!(!space.is_ascii_control());
assert!(lf.is_ascii_control());
assert!(esc.is_ascii_control());

Trait Implementations

impl Clone for char

fn clone(&self) -> char

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl TryFrom<u32> for char

type Error = CharTryFromError

The type returned in the event of a conversion error.

fn try_from(i: u32) -> Result<char, <char as TryFrom<u32>>::Error>

Performs the conversion.

impl Hash for char

fn hash<H>(&self, state: &mut H) where
    H: Hasher, 

Feeds this value into the given [Hasher].

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given [Hasher].

impl Copy for char

impl Default for char

fn default() -> char

Returns the default value of \x00

impl Eq for char

impl<'a> Pattern<'a> for char

Searches for chars that are equal to a given char

type Searcher = CharSearcher<'a>

🔬 This is a nightly-only experimental API. (pattern #27721)

API not fully fleshed out and ready to be stabilized

Associated searcher for this pattern

fn into_searcher(self, haystack: &'a str) -> <char as Pattern<'a>>::Searcher

🔬 This is a nightly-only experimental API. (pattern #27721)

API not fully fleshed out and ready to be stabilized

Constructs the associated searcher from self and the haystack to search in.

fn is_contained_in(self, haystack: &'a str) -> bool

🔬 This is a nightly-only experimental API. (pattern #27721)

API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches anywhere in the haystack

fn is_prefix_of(self, haystack: &'a str) -> bool

🔬 This is a nightly-only experimental API. (pattern #27721)

API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the front of the haystack

fn is_suffix_of(self, haystack: &'a str) -> bool where
    <char as Pattern<'a>>::Searcher: ReverseSearcher<'a>, 

🔬 This is a nightly-only experimental API. (pattern #27721)

API not fully fleshed out and ready to be stabilized

Checks whether the pattern matches at the back of the haystack

impl Display for char

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl PartialEq<char> for char

fn eq(&self, other: &char) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &char) -> bool

This method tests for !=.

impl PartialOrd<char> for char

fn partial_cmp(&self, other: &char) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &char) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &char) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn ge(&self, other: &char) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

fn gt(&self, other: &char) -> bool

This method tests greater than (for self and other) and is used by the > operator.

impl Debug for char

fn fmt(&self, f: &mut Formatter) -> Result<(), Error>

Formats the value using the given formatter.

impl From<u8> for char

Maps a byte in 0x00..=0xFF to a char whose code point has the same value, in U+0000..=U+00FF.

Unicode is designed such that this effectively decodes bytes with the character encoding that IANA calls ISO-8859-1. This encoding is compatible with ASCII.

Note that this is different from ISO/IEC 8859-1 a.k.a. ISO 8859-1 (with one less hyphen), which leaves some "blanks", byte values that are not assigned to any character. ISO-8859-1 (the IANA one) assigns them to the C0 and C1 control codes.

Note that this is also different from Windows-1252 a.k.a. code page 1252, which is a superset ISO/IEC 8859-1 that assigns some (not all!) blanks to punctuation and various Latin characters.

To confuse things further, on the Web ascii, iso-8859-1, and windows-1252 are all aliases for a superset of Windows-1252 that fills the remaining blanks with corresponding C0 and C1 control codes.

fn from(i: u8) -> char

Converts a u8 into a char.

Examples

use std::mem;

fn main() {
    let u = 32 as u8;
    let c = char::from(u);
    assert!(4 == mem::size_of_val(&c))
}

impl Ord for char

fn cmp(&self, other: &char) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

🔬 This is a nightly-only experimental API. (clamp #44095)

Restrict a value to a certain interval.

impl FromStr for char

type Err = ParseCharError

The associated error which can be returned from parsing.

fn from_str(s: &str) -> Result<char, <char as FromStr>::Err>

Parses a string s to return a value of this type.

impl AsciiExt for char

type Owned = char

Deprecated since 1.26.0:

use inherent methods instead

Container type for copied ASCII characters.

fn is_ascii(&self) -> bool

Deprecated since 1.26.0:

use inherent methods instead

Checks if the value is within the ASCII range.

fn to_ascii_uppercase(&self) -> Self::Owned

Deprecated since 1.26.0:

use inherent methods instead

Makes a copy of the value in its ASCII upper case equivalent.

fn to_ascii_lowercase(&self) -> Self::Owned

Deprecated since 1.26.0:

use inherent methods instead

Makes a copy of the value in its ASCII lower case equivalent.

fn eq_ignore_ascii_case(&self, o: &Self) -> bool

Deprecated since 1.26.0:

use inherent methods instead

Checks that two values are an ASCII case-insensitive match.

fn make_ascii_uppercase(&mut self)

Deprecated since 1.26.0:

use inherent methods instead

Converts this type to its ASCII upper case equivalent in-place.

fn make_ascii_lowercase(&mut self)

Deprecated since 1.26.0:

use inherent methods instead

Converts this type to its ASCII lower case equivalent in-place.