The lowest valid code point a char can have, '\0'.

Unlike integer types, char actually has a gap in the middle, meaning that the range of possible chars is smaller than you might expect. Ranges of char will automatically hop this gap for you:

#![feature(char_min)]
let dist = u32::from(char::MAX) - u32::from(char::MIN);
let size = (char::MIN..=char::MAX).count() as u32;
assert!(size < dist);

Despite this gap, the MIN and MAX values can be used as bounds for all char values.

Examples

#![feature(char_min)]
let c: char = something_which_returns_char();
assert!(char::MIN <= c);

let value_at_min = u32::from(char::MIN);
assert_eq!(char::from_u32(value_at_min), Some('\0'));

The highest valid code point a char can have, '\u{10FFFF}'.

Unlike integer types, char actually has a gap in the middle, meaning that the range of possible chars is smaller than you might expect. Ranges of char will automatically hop this gap for you:

#![feature(char_min)]
let dist = u32::from(char::MAX) - u32::from(char::MIN);
let size = (char::MIN..=char::MAX).count() as u32;
assert!(size < dist);

Despite this gap, the MIN and MAX values can be used as bounds for all char values.

Examples

let c: char = something_which_returns_char();
assert!(c <= char::MAX);

let value_at_max = u32::from(char::MAX);
assert_eq!(char::from_u32(value_at_max), Some('\u{10FFFF}'));
assert_eq!(char::from_u32(value_at_max + 1), None);

U+FFFD REPLACEMENT CHARACTER (�) 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.

The version of Unicode that the Unicode parts of char and str methods are based on.

New versions of Unicode are released regularly and subsequently all methods in the standard library depending on Unicode are updated. Therefore the behavior of some char and str methods and the value of this constant changes over time. This is not considered to be a breaking change.

The version numbering scheme is explained in Unicode 11.0 or later, Section 3.1 Versions of the Unicode Standard.

Creates an iterator over the UTF-16 encoded code points in iter, returning unpaired surrogates as Errs.

Examples

Basic usage:

// 𝄞mus<invalid>ic<invalid>
let v = [
    0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0xDD1E, 0x0069, 0x0063, 0xD834,
];

assert_eq!(
    char::decode_utf16(v)
        .map(|r| r.map_err(|e| e.unpaired_surrogate()))
        .collect::<Vec<_>>(),
    vec![
        Ok('𝄞'),
        Ok('m'), Ok('u'), Ok('s'),
        Err(0xDD1E),
        Ok('i'), Ok('c'),
        Err(0xD834)
    ]
);

A lossy decoder can be obtained by replacing Err results with the replacement character:

// 𝄞mus<invalid>ic<invalid>
let v = [
    0xD834, 0xDD1E, 0x006d, 0x0075, 0x0073, 0xDD1E, 0x0069, 0x0063, 0xD834,
];

assert_eq!(
    char::decode_utf16(v)
       .map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
       .collect::<String>(),
    "𝄞mus�ic�"
);

Converts a u32 to a char.

Note that all chars are valid u32s, and can be cast to one with as:

let c = '💯';
let i = c as u32;

assert_eq!(128175, i);

However, the reverse is not true: not all valid u32s are valid chars. from_u32() will return None if the input is not a valid value for a char.

For an unsafe version of this function which ignores these checks, see from_u32_unchecked.

Examples

Basic usage:

let c = char::from_u32(0x2764);

assert_eq!(Some('❤'), c);

Returning None when the input is not a valid char:

let c = char::from_u32(0x110000);

assert_eq!(None, c);

Converts a u32 to a char, ignoring validity.

Note that all chars are valid u32s, and can be cast to one with as:

let c = '💯';
let i = c as u32;

assert_eq!(128175, i);

However, the reverse is not true: not all valid u32s are valid chars. from_u32_unchecked() will ignore this, and blindly cast to char, possibly creating an invalid one.

Safety

This function is unsafe, as it may construct invalid char values.

For a safe version of this function, see the from_u32 function.

Examples

Basic usage:

let c = unsafe { char::from_u32_unchecked(0x2764) };

assert_eq!('❤', c);

Converts a digit in the given radix to a char.

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.

from_digit() will return None if the input is not a digit in the given radix.

Panics

Panics if given a radix larger than 36.

Examples

Basic usage:

let c = char::from_digit(4, 10);

assert_eq!(Some('4'), c);

// Decimal 11 is a single digit in base 16
let c = char::from_digit(11, 16);

assert_eq!(Some('b'), c);

Returning None when the input is not a digit:

let c = char::from_digit(20, 10);

assert_eq!(None, c);

Passing a large radix, causing a panic:

// this panics
let _c = char::from_digit(1, 37);

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:

// this panics
'1'.is_digit(37);

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:

// this panics
let _ = '1'.to_digit(37);

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}");

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");

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(), "\\\"");

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());

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

That number of code units is always either 1 or 2, for unicode scalar values in the basic multilingual plane or supplementary planes respectively.

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);

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:

let mut b = [0; 1];

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

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:

let mut b = [0; 1];

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

Returns true if this char has the Alphabetic property.

Alphabetic is described in Chapter 4 (Character Properties) of the Unicode Standard and specified in the Unicode Character Database DerivedCoreProperties.txt.

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());

Returns true if this char has the Lowercase property.

Lowercase is described in Chapter 4 (Character Properties) of the Unicode Standard and specified in the Unicode Character Database DerivedCoreProperties.txt.

Examples

Basic usage:

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

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

In a const context:

#![feature(const_unicode_case_lookup)]
const CAPITAL_DELTA_IS_LOWERCASE: bool = 'Δ'.is_lowercase();
assert!(!CAPITAL_DELTA_IS_LOWERCASE);

Returns true if this char has the Uppercase property.

Uppercase is described in Chapter 4 (Character Properties) of the Unicode Standard and specified in the Unicode Character Database DerivedCoreProperties.txt.

Examples

Basic usage:

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

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

In a const context:

#![feature(const_unicode_case_lookup)]
const CAPITAL_DELTA_IS_UPPERCASE: bool = 'Δ'.is_uppercase();
assert!(CAPITAL_DELTA_IS_UPPERCASE);

Returns true if this char has the White_Space property.

White_Space is specified in the Unicode Character Database PropList.txt.

Examples

Basic usage:

assert!(' '.is_whitespace());

// line break
assert!('\n'.is_whitespace());

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

assert!(!'越'.is_whitespace());

Returns true if this char satisfies either is_alphabetic() or is_numeric().

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());

Returns true if this char has the general category for control codes.

Control codes (code points with the general category of Cc) are described in Chapter 4 (Character Properties) of the Unicode Standard and specified in the Unicode Character Database UnicodeData.txt.

Examples

Basic usage:

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

Returns true if this char has one of the general categories for numbers.

The general categories for numbers (Nd for decimal digits, Nl for letter-like numeric characters, and No for other numeric characters) are specified in the Unicode Character Database UnicodeData.txt.

This method doesn’t cover everything that could be considered a number, e.g. ideographic numbers like ‘三’. If you want everything including characters with overlapping purposes then you might want to use a unicode or language-processing library that exposes the appropriate character properties instead of looking at the unicode categories.

If you want to parse ASCII decimal digits (0-9) or ASCII base-N, use is_ascii_digit or is_digit instead.

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());
assert!(!'三'.is_numeric());

Returns an iterator that yields the lowercase mapping of this char as one or more chars.

If this char does not have a lowercase mapping, the iterator yields the same char.

If this char has a one-to-one lowercase mapping given by the Unicode Character Database UnicodeData.txt, the iterator yields that char.

If this char requires special considerations (e.g. multiple chars) the iterator yields the char(s) given by SpecialCasing.txt.

This operation performs an unconditional mapping without tailoring. That is, the conversion is independent of context and language.

In the Unicode Standard, Chapter 4 (Character Properties) discusses case mapping in general and Chapter 3 (Conformance) discusses the default algorithm for case conversion.

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");

Returns an iterator that yields the uppercase mapping of this char as one or more chars.

If this char does not have an uppercase mapping, the iterator yields the same char.

If this char has a one-to-one uppercase mapping given by the Unicode Character Database UnicodeData.txt, the iterator yields that char.

If this char requires special considerations (e.g. multiple chars) the iterator yields the char(s) given by SpecialCasing.txt.

This operation performs an unconditional mapping without tailoring. That is, the conversion is independent of context and language.

In the Unicode Standard, Chapter 4 (Character Properties) discusses case mapping in general and Chapter 3 (Conformance) discusses the default algorithm for case conversion.

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.

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());

Returns Some if the value is within the ASCII range, or None if it’s not.

This is preferred to Self::is_ascii when you’re passing the value along to something else that can take ascii::Char rather than needing to check again for itself whether the value is in ASCII.

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());

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());

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));

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);

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);

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 = '\x1b';

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());

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 = '\x1b';

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());

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 = '\x1b';

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());

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 = '\x1b';

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());

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 = '\x1b';

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());

Checks if the value is an ASCII octal digit: U+0030 ‘0’ ..= U+0037 ‘7’.

Examples

#![feature(is_ascii_octdigit)]

let uppercase_a = 'A';
let a = 'a';
let zero = '0';
let seven = '7';
let nine = '9';
let percent = '%';
let lf = '\n';

assert!(!uppercase_a.is_ascii_octdigit());
assert!(!a.is_ascii_octdigit());
assert!(zero.is_ascii_octdigit());
assert!(seven.is_ascii_octdigit());
assert!(!nine.is_ascii_octdigit());
assert!(!percent.is_ascii_octdigit());
assert!(!lf.is_ascii_octdigit());

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 = '\x1b';

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());

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 = '\x1b';

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());

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 = '\x1b';

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());

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 = '\x1b';

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());

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 = '\x1b';

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());

Returns the default value of \x00

Allocates an owned String from a single character.

Example

let c: char = 'a';
let s: String = String::from(c);
assert_eq!("a", &s[..]);

Converts a char into a u128.

Examples

use std::mem;

let c = '⚙';
let u = u128::from(c);
assert!(16 == mem::size_of_val(&u))

Converts a char into a u32.

Examples

use std::mem;

let c = 'c';
let u = u32::from(c);
assert!(4 == mem::size_of_val(&u))

Converts a char into a u64.

Examples

use std::mem;

let c = '👤';
let u = u64::from(c);
assert!(8 == mem::size_of_val(&u))

Converts a u8 into a char.

Examples

use std::mem;

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

Tries to convert a char into a u16.

Examples

let trans_rights = '⚧'; // U+26A7
let ninjas = '🥷'; // U+1F977
assert_eq!(u16::try_from(trans_rights), Ok(0x26A7_u16));
assert!(u16::try_from(ninjas).is_err());

Tries to convert a char into a u8.

Examples

let a = 'ÿ'; // U+00FF
let b = 'Ā'; // U+0100
assert_eq!(u8::try_from(a), Ok(0xFF_u8));
assert!(u8::try_from(b).is_err());

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.