# struct Char

- Char
- Value
- Object

##
Overview

A `Char` represents a Unicode code point. It occupies 32 bits.

It is created by enclosing an UTF-8 character in single quotes.

    'a'
    'z'
    '0'
    '_'
    'あ'

You can use a backslash to denote some characters:

    '\'' # single quote
    '\\' # backslash
    '\e' # escape
    '\f' # form feed
    '\n' # newline
    '\r' # carriage return
    '\t' # tab
    '\v' # vertical tab

You can use a backslash followed by an u and four hexadecimal characters to denote a unicode codepoint written:

    '\u0041' # == 'A'

Or you can use curly braces and specify up to four hexadecimal numbers:

    '\u{41}' # == 'A'

See `Char` literals in the language reference.

##
Included Modules

- Comparable(Char)
- Steppable

##
Defined in:

char.cr
char/reader.cr
primitives.cr

##
Constant Summary

MAX = `1114111.unsafe_chr`

  The maximum character.

MAX_CODEPOINT = `1114111`

  The maximum valid codepoint for a character.

REPLACEMENT = `'�'`

  The replacement character, used on invalid UTF-8 byte sequences.

ZERO = `'\0'`

  The character representing the end of a C string.

##
Instance Method Summary

- #!=(other : Char) : Bool

  Returns `true` if `self`'s codepoint is not equal to other's codepoint.

- #+(str : String) : String

  Concatenates this char and string.

- #+(other : Int) : Char

  Returns a char that has this char's codepoint plus other.

- #-(other : Char) : Int32

  Returns the difference of the codepoint values of this char and other.

- #-(other : Int) : Char

  Returns a char that has this char's codepoint minus other.

- #<(other : Char) : Bool

  Returns `true` if `self`'s codepoint is less than other's codepoint.

- #<=(other : Char) : Bool

  Returns `true` if `self`'s codepoint is less than or equal to other's codepoint.

- #<=>(other : Char)

  The comparison operator.

- #==(other : Char) : Bool

  Returns `true` if `self`'s codepoint is equal to other's codepoint.

- #===(byte : Int)

  Returns `true` if the codepoint is equal to byte ignoring the type.

- #>(other : Char) : Bool

  Returns `true` if `self`'s codepoint is greater than other's codepoint.

- #>=(other : Char) : Bool

  Returns `true` if `self`'s codepoint is greater than or equal to other's codepoint.

- #alphanumeric? : Bool

  Returns `true` if this char is a letter or a number according to unicode.

- #ascii? : Bool

  Returns `true` if this char is an ASCII character (codepoint is in (0..127))

- #ascii_alphanumeric? : Bool

  Returns `true` if this char is an ASCII letter or number ('0' to '9', 'a' to 'z', 'A' to 'Z').

- #ascii_control? : Bool

  Returns `true` if this char is an ASCII control character.

- #ascii_letter? : Bool

  Returns `true` if this char is an ASCII letter ('a' to 'z', 'A' to 'Z').

- #ascii_lowercase? : Bool

  Returns `true` if this char is a lowercase ASCII letter.

- #ascii_number?(base : Int = 10) : Bool

  Returns `true` if this char is an ASCII number in specified base.

- #ascii_uppercase? : Bool

  Returns `true` if this char is an ASCII uppercase letter.

- #ascii_whitespace? : Bool

  Returns `true` if this char is an ASCII whitespace.

- #bytes : Array(UInt8)

  Returns this char bytes as encoded by UTF-8, as an `Array(UInt8)`.

- #bytesize : Int32

  Returns the number of UTF-8 bytes in this char.

- #clone
- #control? : Bool

  Returns `true` if this char is a control character according to unicode.

- #downcase(io : IO, options : Unicode::CaseOptions = :none) : Nil

  Writes the downcase equivalent of this char to the given io.

- #downcase(options : Unicode::CaseOptions = :none) : Char

  Returns the downcase equivalent of this char.

- #downcase(options : Unicode::CaseOptions = :none, &)

  Yields each char for the downcase equivalent of this char.

- #dump(io)

  Returns a representation of `self` as an ASCII-compatible Crystal char literal, wrapped in single quotes.

- #dump : String

  Returns a representation of `self` as an ASCII-compatible Crystal char literal, wrapped in single quotes.

- #each_byte(&) : Nil

  Yields each of the bytes of this char as encoded by UTF-8.

- #hash(hasher)

  See `Object#hash(hasher)`

- #hex? : Bool

  Returns `true` if this char is an ASCII hex digit ('0' to '9', 'a' to 'f', 'A' to 'F').

- #in_set?(*sets : String) : Bool

  Returns `true` if this char is matched by the given sets.

- #inspect(io : IO) : Nil

  Returns a representation of `self` as a Crystal char literal, wrapped in single quotes.

- #inspect : String

  Returns a representation of `self` as a Crystal char literal, wrapped in single quotes.

- #letter? : Bool

  Returns `true` if this char is a letter.

- #lowercase? : Bool

  Returns `true` if this char is a lowercase letter.

- #mark? : Bool

  Returns `true` if this char is a mark character according to unicode.

- #number? : Bool

  Returns `true` if this char is a number according to unicode.

- #ord : Int32

  Returns the codepoint of this char.

- #pred : Char

  Returns the predecessor codepoint before this one.

- #printable?

  Returns `true` if this char is a printable character.

- #step(*, to limit = nil, exclusive : Bool = false, &)

  Performs a `#step` in the direction of the limit.

- #step(*, to limit = nil, exclusive : Bool = false)

  Performs a `#step` in the direction of the limit.

- #succ : Char

  Returns the successor codepoint after this one.

- #titlecase(io : IO, options : Unicode::CaseOptions = :none) : Nil

  Writes the titlecase equivalent of this char to the given io.

- #titlecase(options : Unicode::CaseOptions = :none) : Char

  Returns the titlecase equivalent of this char.

- #titlecase(options : Unicode::CaseOptions = :none, &)

  Yields each char for the titlecase equivalent of this char.

- #titlecase? : Bool

  Returns `true` if this char is a titlecase character, i.e.

- #to_f : Float64

  Returns the integer value of this char as a float if it's an ASCII char denoting a digit, raises otherwise.

- #to_f32 : Float32

  See also: `#to_f`.

- #to_f32? : Float32 | Nil

  See also: `#to_f?`.

- #to_f64 : Float64

  Same as `#to_f`.

- #to_f64? : Float64 | Nil

  Same as `#to_f?`.

- #to_f? : Float64 | Nil

  Returns the integer value of this char as a float if it's an ASCII char denoting a digit, `nil` otherwise.

- #to_i(base : Int = 10) : Int32

  Returns the integer value of this char if it's an ASCII char denoting a digit in base, raises otherwise.

- #to_i128(base : Int = 10)

  See also: `#to_i`.

- #to_i128?(base : Int = 10)

  See also: `#to_i?`.

- #to_i16(base : Int = 10)

  See also: `#to_i`.

- #to_i16?(base : Int = 10)

  See also: `#to_i?`.

- #to_i32(base : Int = 10) : Int32

  Same as `#to_i`.

- #to_i32?(base : Int = 10) : Int32 | Nil

  Same as `#to_i?`.

- #to_i64(base : Int = 10)

  See also: `#to_i`.

- #to_i64?(base : Int = 10)

  See also: `#to_i?`.

- #to_i8(base : Int = 10)

  See also: `#to_i`.

- #to_i8?(base : Int = 10)

  See also: `#to_i?`.

- #to_i?(base : Int = 10) : Int32 | Nil

  Returns the integer value of this char if it's an ASCII char denoting a digit in base, `nil` otherwise.

- #to_s(io : IO) : Nil

  Appends this char to the given `IO`.

- #to_s : String

  Returns this char as a string containing this char as a single character.

- #to_u128(base : Int = 10)

  See also: `#to_i`.

- #to_u128?(base : Int = 10)

  See also: `#to_i?`.

- #to_u16(base : Int = 10)

  See also: `#to_i`.

- #to_u16?(base : Int = 10)

  See also: `#to_i?`.

- #to_u32(base : Int = 10)

  See also: `#to_i`.

- #to_u32?(base : Int = 10)

  See also: `#to_i?`.

- #to_u64(base : Int = 10)

  See also: `#to_i`.

- #to_u64?(base : Int = 10)

  See also: `#to_i?`.

- #to_u8(base : Int = 10)

  See also: `#to_i`.

- #to_u8?(base : Int = 10)

  See also: `#to_i?`.

- #unicode_escape(io : IO) : Nil

  Returns the Unicode escape sequence representing this character.

- #unicode_escape : String

  Returns the Unicode escape sequence representing this character.

- #upcase(io : IO, options : Unicode::CaseOptions = :none) : Nil

  Writes the upcase equivalent of this char to the given io.

- #upcase(options : Unicode::CaseOptions = :none) : Char

  Returns the upcase equivalent of this char.

- #upcase(options : Unicode::CaseOptions = :none, &)

  Yields each char for the upcase equivalent of this char.

- #uppercase? : Bool

  Returns `true` if this char is an uppercase letter.

- #whitespace? : Bool

  Returns `true` if this char is a whitespace according to unicode.

### Instance methods inherited from module `Steppable`

step(*, to limit = nil, by step, exclusive : Bool = false, &) : Nil
step(*, to limit = nil, by step, exclusive : Bool = false) step

### Instance methods inherited from module `Comparable(Char)`

<(other : T) : Bool <, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) : Bool >, >=(other : T) >=, clamp(min, max)
clamp(range : Range) clamp

### Instance methods inherited from struct `Value`

==(other : JSON::Any)
==(other : YAML::Any)
==(other) ==, dup dup

### Instance methods inherited from class `Object`

! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)
===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil!(message)
not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as

### Class methods inherited from class `Object`

from_json(string_or_io, root : String)
from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml

### Macros inherited from class `Object`

class_getter(*names, &block) class_getter, class_getter!(*names) class_getter!, class_getter?(*names, &block) class_getter?, class_property(*names, &block) class_property, class_property!(*names) class_property!, class_property?(*names, &block) class_property?, class_setter(*names) class_setter, def_clone def_clone, def_equals(*fields) def_equals, def_equals_and_hash(*fields) def_equals_and_hash, def_hash(*fields) def_hash, delegate(*methods, to object) delegate, forward_missing_to(delegate) forward_missing_to, getter(*names, &block) getter, getter!(*names) getter!, getter?(*names, &block) getter?, property(*names, &block) property, property!(*names) property!, property?(*names, &block) property?, setter(*names) setter

##
Instance Method Detail

def !=(other : Char) : Bool #

Returns `true` if `self`'s codepoint is not equal to other's codepoint.

def +(str : String) : String #

Concatenates this char and string.

    'f' + "oo" # => "foo"

def +(other : Int) : Char #

Returns a char that has this char's codepoint plus other.

    'a' + 1 # => 'b'
    'a' + 2 # => 'c'

def -(other : Char) : Int32 #

Returns the difference of the codepoint values of this char and other.

    'a' - 'a' # => 0
    'b' - 'a' # => 1
    'c' - 'a' # => 2

def -(other : Int) : Char #

Returns a char that has this char's codepoint minus other.

    'c' - 1 # => 'b'
    'c' - 2 # => 'a'

def <(other : Char) : Bool #

Returns `true` if `self`'s codepoint is less than other's codepoint.

def <=(other : Char) : Bool #

Returns `true` if `self`'s codepoint is less than or equal to other's codepoint.

def <=>(other : Char) #

The comparison operator.

Returns the difference of the codepoint values of `self` and other. The result is either negative, `0` or positive based on whether `other`'s codepoint is less, equal, or greater than `self`'s codepoint.

    'a' <=> 'c' # => -2
    'z' <=> 'z' # => 0
    'c' <=> 'a' # => 2

def ==(other : Char) : Bool #

Returns `true` if `self`'s codepoint is equal to other's codepoint.

def ===(byte : Int) #

Returns `true` if the codepoint is equal to byte ignoring the type.

    'c'.ord       # => 99
    'c' === 99_u8 # => true
    'c' === 99    # => true
    'z' === 99    # => false

def >(other : Char) : Bool #

Returns `true` if `self`'s codepoint is greater than other's codepoint.

def >=(other : Char) : Bool #

Returns `true` if `self`'s codepoint is greater than or equal to other's codepoint.

def alphanumeric? : Bool #

Returns `true` if this char is a letter or a number according to unicode.

    'c'.alphanumeric? # => true
    '8'.alphanumeric? # => true
    '.'.alphanumeric? # => false

def ascii? : Bool #

Returns `true` if this char is an ASCII character (codepoint is in (0..127))

def ascii_alphanumeric? : Bool #

Returns `true` if this char is an ASCII letter or number ('0' to '9', 'a' to 'z', 'A' to 'Z').

    'c'.ascii_alphanumeric? # => true
    '8'.ascii_alphanumeric? # => true
    '.'.ascii_alphanumeric? # => false

def ascii_control? : Bool #

Returns `true` if this char is an ASCII control character.

This includes the C0 control codes (`U+0000` through `U+001F`) and the Delete character (`U+007F`).

    ('\u0000'..'\u0019').each do |char|
      char.control? # => true
    end

    ('\u007F'..'\u009F').each do |char|
      char.control? # => true
    end

def ascii_letter? : Bool #

Returns `true` if this char is an ASCII letter ('a' to 'z', 'A' to 'Z').

    'c'.ascii_letter? # => true
    'á'.ascii_letter? # => false
    '8'.ascii_letter? # => false

def ascii_lowercase? : Bool #

Returns `true` if this char is a lowercase ASCII letter.

    'c'.ascii_lowercase? # => true
    'ç'.lowercase?       # => true
    'G'.ascii_lowercase? # => false
    '.'.ascii_lowercase? # => false

def ascii_number?(base : Int = 10) : Bool #

Returns `true` if this char is an ASCII number in specified base.

Base can be from 2 to 36 with digits from '0' to '9' and 'a' to 'z' or 'A' to 'Z'.

    '4'.ascii_number?     # => true
    'z'.ascii_number?     # => false
    'z'.ascii_number?(36) # => true

def ascii_uppercase? : Bool #

Returns `true` if this char is an ASCII uppercase letter.

    'H'.ascii_uppercase? # => true
    'Á'.ascii_uppercase? # => false
    'c'.ascii_uppercase? # => false
    '.'.ascii_uppercase? # => false

def ascii_whitespace? : Bool #

Returns `true` if this char is an ASCII whitespace.

    ' '.ascii_whitespace?  # => true
    '\t'.ascii_whitespace? # => true
    'b'.ascii_whitespace?  # => false

def bytes : Array(UInt8) #

Returns this char bytes as encoded by UTF-8, as an `Array(UInt8)`.

    'a'.bytes # => [97]
    'あ'.bytes # => [227, 129, 130]

def bytesize : Int32 #

Returns the number of UTF-8 bytes in this char.

    'a'.bytesize # => 1
    '好'.bytesize # => 3

def clone #
def control? : Bool #

Returns `true` if this char is a control character according to unicode.

def downcase(io : IO, options : Unicode::CaseOptions = :none) : Nil #

Writes the downcase equivalent of this char to the given io.

This method takes into account the possibility that an downcase version of a char might result in multiple chars, like for 'İ', which results in 'i' and a dot mark.

    'Z'.downcase(STDOUT)                             # prints "z"
    'ς'.downcase(STDOUT, Unicode::CaseOptions::Fold) # prints "σ"
    'ẞ'.downcase(STDOUT, Unicode::CaseOptions::Fold) # prints "ss"
    'ᾈ'.downcase(STDOUT, Unicode::CaseOptions::Fold) # prints "ἀι"

def downcase(options : Unicode::CaseOptions = :none) : Char #

Returns the downcase equivalent of this char.

Note that this only works for characters whose downcase equivalent yields a single codepoint. There are a few characters, like 'İ', than when downcased result in multiple characters (in this case: 'I' and the dot mark).

For more correct behavior see the overloads that receive a block or an `IO`.

    'Z'.downcase # => 'z'
    'x'.downcase # => 'x'
    '.'.downcase # => '.'

If `options.fold?` is true, then returns the case-folded equivalent instead. Note that this will return `self` if a multiple-character case folding exists, even if a separate single-character transformation is also defined in Unicode.

    'Z'.downcase(Unicode::CaseOptions::Fold) # => 'z'
    'x'.downcase(Unicode::CaseOptions::Fold) # => 'x'
    'ς'.downcase(Unicode::CaseOptions::Fold) # => 'σ'
    'ꭰ'.downcase(Unicode::CaseOptions::Fold) # => 'Ꭰ'
    'ẞ'.downcase(Unicode::CaseOptions::Fold) # => 'ẞ' # not U+00DF 'ß'
    'ᾈ'.downcase(Unicode::CaseOptions::Fold) # => "ᾈ" # not U+1F80 'ᾀ'

def downcase(options : Unicode::CaseOptions = :none, &) #

Yields each char for the downcase equivalent of this char.

This method takes into account the possibility that an downcase version of a char might result in multiple chars, like for 'İ', which results in 'i' and a dot mark.

    'Z'.downcase { |v| puts v }                             # prints 'z'
    'ς'.downcase(Unicode::CaseOptions::Fold) { |v| puts v } # prints 'σ'
    'ẞ'.downcase(Unicode::CaseOptions::Fold) { |v| puts v } # prints 's', 's'
    'ᾈ'.downcase(Unicode::CaseOptions::Fold) { |v| puts v } # prints 'ἀ', 'ι'

def dump(io) #

Returns a representation of `self` as an ASCII-compatible Crystal char literal, wrapped in single quotes.

Non-printable characters (see `#printable?`) and non-ASCII characters (codepoints larger `U+007F`) are escaped.

    'a'.dump      # => "'a'"
    '\t'.dump     # => "'\\t'"
    'あ'.dump      # => "'\\u3042'"
    '\u0012'.dump # => "'\\u0012'"
    '😀'.dump      # => "'\\u{1F600}'"

See `#unicode_escape` for the format used to escape characters without a special escape sequence.

- `#inspect` only escapes non-printable characters.

def dump : String #

Returns a representation of `self` as an ASCII-compatible Crystal char literal, wrapped in single quotes.

Non-printable characters (see `#printable?`) and non-ASCII characters (codepoints larger `U+007F`) are escaped.

    'a'.dump      # => "'a'"
    '\t'.dump     # => "'\\t'"
    'あ'.dump      # => "'\\u3042'"
    '\u0012'.dump # => "'\\u0012'"
    '😀'.dump      # => "'\\u{1F600}'"

See `#unicode_escape` for the format used to escape characters without a special escape sequence.

- `#inspect` only escapes non-printable characters.

def each_byte(&) : Nil #

Yields each of the bytes of this char as encoded by UTF-8.

    puts "'a'"
    'a'.each_byte do |byte|
      puts byte
    end
    puts

    puts "'あ'"
    'あ'.each_byte do |byte|
      puts byte
    end

Output:

    'a'
    97

    'あ'
    227
    129
    130

def hash(hasher) #

See `Object#hash(hasher)`

def hex? : Bool #

Returns `true` if this char is an ASCII hex digit ('0' to '9', 'a' to 'f', 'A' to 'F').

    '5'.hex? # => true
    'a'.hex? # => true
    'F'.hex? # => true
    'g'.hex? # => false

def in_set?(*sets : String) : Bool #

Returns `true` if this char is matched by the given sets.

Each parameter defines a set, the character is matched against the intersection of those, in other words it needs to match all sets.

If a set starts with a ^, it is negated. The sequence c1-c2 means all characters between and including c1 and c2 and is known as a range.

The backslash character \ can be used to escape ^ or - and is otherwise ignored unless it appears at the end of a range or set.

    'l'.in_set? "lo"          # => true
    'l'.in_set? "lo", "o"     # => false
    'l'.in_set? "hello", "^l" # => false
    'l'.in_set? "j-m"         # => true

    '^'.in_set? "\\^aeiou" # => true
    '-'.in_set? "a\\-eo"   # => true

    '\\'.in_set? "\\"    # => true
    '\\'.in_set? "\\A"   # => false
    '\\'.in_set? "X-\\w" # => true

def inspect(io : IO) : Nil #

Returns a representation of `self` as a Crystal char literal, wrapped in single quotes.

Non-printable characters (see `#printable?`) are escaped.

    'a'.inspect      # => "'a'"
    '\t'.inspect     # => "'\\t'"
    'あ'.inspect      # => "'あ'"
    '\u0012'.inspect # => "'\\u0012'"
    '😀'.inspect      # => "'\u{1F600}'"

See `#unicode_escape` for the format used to escape characters without a special escape sequence.

- `#dump` additionally escapes all non-ASCII characters.

def inspect : String #

Returns a representation of `self` as a Crystal char literal, wrapped in single quotes.

Non-printable characters (see `#printable?`) are escaped.

    'a'.inspect      # => "'a'"
    '\t'.inspect     # => "'\\t'"
    'あ'.inspect      # => "'あ'"
    '\u0012'.inspect # => "'\\u0012'"
    '😀'.inspect      # => "'\u{1F600}'"

See `#unicode_escape` for the format used to escape characters without a special escape sequence.

- `#dump` additionally escapes all non-ASCII characters.

def letter? : Bool #

Returns `true` if this char is a letter.

All codepoints in the Unicode General Category `L` (Letter) are considered a letter.

    'c'.letter? # => true
    'á'.letter? # => true
    '8'.letter? # => false

def lowercase? : Bool #

Returns `true` if this char is a lowercase letter.

    'c'.lowercase? # => true
    'ç'.lowercase? # => true
    'G'.lowercase? # => false
    '.'.lowercase? # => false
    'ǲ'.lowercase? # => false

def mark? : Bool #

Returns `true` if this char is a mark character according to unicode.

def number? : Bool #

Returns `true` if this char is a number according to unicode.

    '1'.number? # => true
    'a'.number? # => false

def ord : Int32 #

Returns the codepoint of this char.

The codepoint is the integer representation. The Universal Coded Character Set (UCS) standard, commonly known as Unicode, assigns names and meanings to numbers, these numbers are called codepoints.

For values below and including 127 this matches the ASCII codes and thus its byte representation.

    'a'.ord      # => 97
    '\0'.ord     # => 0
    '\u007f'.ord # => 127
    '☃'.ord      # => 9731

def pred : Char #

Returns the predecessor codepoint before this one.

This can be used for iterating a range of characters (see `Range#each`).

    'b'.pred # => 'a'
    'ぃ'.pred # => 'あ'

This does not always return `codepoint - 1`. There is a gap in the range of Unicode scalars: The surrogate codepoints `U+D800` through `U+DFFF`.

    '\uE000'.pred # => '\uD7FF'

Raises `OverflowError` for `Char::ZERO`.

- `#succ` returns the successor codepoint.

def printable? #

Returns `true` if this char is a printable character.

There is no universal definition of printable characters in Unicode. For the purpose of this method, all characters with a visible glyph and the ASCII whitespace (`` ) are considered printable.

This means characters which are `#control?` or `#whitespace?` (except for `` ) are non-printable.

def step(*, to limit = nil, exclusive : Bool = false, &) #

Performs a `#step` in the direction of the limit. For instance:

    'd'.step(to: 'a').to_a # => ['d', 'c', 'b', 'a']
    'a'.step(to: 'd').to_a # => ['a', 'b', 'c', 'd']

def step(*, to limit = nil, exclusive : Bool = false) #

Performs a `#step` in the direction of the limit. For instance:

    'd'.step(to: 'a').to_a # => ['d', 'c', 'b', 'a']
    'a'.step(to: 'd').to_a # => ['a', 'b', 'c', 'd']

def succ : Char #

Returns the successor codepoint after this one.

This can be used for iterating a range of characters (see `Range#each`).

    'a'.succ # => 'b'
    'あ'.succ # => 'ぃ'

This does not always return `codepoint + 1`. There is a gap in the range of Unicode scalars: The surrogate codepoints `U+D800` through `U+DFFF`.

    '\uD7FF'.succ # => '\uE000'

Raises `OverflowError` for `Char::MAX`.

- `#pred` returns the predecessor codepoint.

def titlecase(io : IO, options : Unicode::CaseOptions = :none) : Nil #

Writes the titlecase equivalent of this char to the given io.

Usually this is equivalent to `#upcase`, but a few precomposed characters consisting of multiple letters may yield a different character sequence where only the first letter is uppercase and the rest lowercase.

This method takes into account the possibility that a titlecase version of a char might result in multiple chars, like for 'ﬄ', which results in 'F', 'f' and 'l'.

    'z'.titlecase(STDOUT) # prints "Z"
    'Ǳ'.titlecase(STDOUT) # prints "ǲ"
    'ﬄ'.titlecase(STDOUT) # prints "Ffl"

def titlecase(options : Unicode::CaseOptions = :none) : Char #

Returns the titlecase equivalent of this char.

Usually this is equivalent to `#upcase`, but a few precomposed characters consisting of multiple letters may return a different character where only the first letter is uppercase and the rest lowercase.

Note that this only works for characters whose titlecase equivalent yields a single codepoint. There are a few characters, like 'ﬄ', than when titlecased result in multiple characters (in this case: 'F', 'f', 'l').

For more correct behavior see the overloads that receive a block or an `IO`.

    'z'.titlecase # => 'Z'
    'X'.titlecase # => 'X'
    '.'.titlecase # => '.'
    'Ǳ'.titlecase # => 'ǲ'
    'ǳ'.titlecase # => 'ǲ'

def titlecase(options : Unicode::CaseOptions = :none, &) #

Yields each char for the titlecase equivalent of this char.

Usually this is equivalent to `#upcase`, but a few precomposed characters consisting of multiple letters may yield a different character sequence where only the first letter is uppercase and the rest lowercase.

This method takes into account the possibility that a titlecase version of a char might result in multiple chars, like for 'ﬄ', which results in 'F', 'f' and 'l'.

    'z'.titlecase { |v| puts v } # prints 'Z'
    'Ǳ'.titlecase { |v| puts v } # prints 'ǲ'
    'ﬄ'.titlecase { |v| puts v } # prints 'F', 'f', 'l'

def titlecase? : Bool #

Returns `true` if this char is a titlecase character, i.e. a ligature consisting of an uppercase letter followed by lowercase characters.

    'ǲ'.titlecase? # => true
    'H'.titlecase? # => false
    'c'.titlecase? # => false

def to_f : Float64 #

Returns the integer value of this char as a float if it's an ASCII char denoting a digit, raises otherwise.

    '1'.to_f # => 1.0
    '8'.to_f # => 8.0
    'c'.to_f # raises ArgumentError

def to_f32 : Float32 #

See also: `#to_f`.

def to_f32? : Float32 | Nil #

See also: `#to_f?`.

def to_f64 : Float64 #

Same as `#to_f`.

def to_f64? : Float64 | Nil #

Same as `#to_f?`.

def to_f? : Float64 | Nil #

Returns the integer value of this char as a float if it's an ASCII char denoting a digit, `nil` otherwise.

    '1'.to_f? # => 1.0
    '8'.to_f? # => 8.0
    'c'.to_f? # => nil

def to_i(base : Int = 10) : Int32 #

Returns the integer value of this char if it's an ASCII char denoting a digit in base, raises otherwise.

    '1'.to_i     # => 1
    '8'.to_i     # => 8
    'c'.to_i     # raises ArgumentError
    '1'.to_i(16) # => 1
    'a'.to_i(16) # => 10
    'f'.to_i(16) # => 15
    'z'.to_i(16) # raises ArgumentError

def to_i128(base : Int = 10) #

See also: `#to_i`.

def to_i128?(base : Int = 10) #

See also: `#to_i?`.

def to_i16(base : Int = 10) #

See also: `#to_i`.

def to_i16?(base : Int = 10) #

See also: `#to_i?`.

def to_i32(base : Int = 10) : Int32 #

Same as `#to_i`.

def to_i32?(base : Int = 10) : Int32 | Nil #

Same as `#to_i?`.

def to_i64(base : Int = 10) #

See also: `#to_i`.

def to_i64?(base : Int = 10) #

See also: `#to_i?`.

def to_i8(base : Int = 10) #

See also: `#to_i`.

def to_i8?(base : Int = 10) #

See also: `#to_i?`.

def to_i?(base : Int = 10) : Int32 | Nil #

Returns the integer value of this char if it's an ASCII char denoting a digit in base, `nil` otherwise.

    '1'.to_i?     # => 1
    '8'.to_i?     # => 8
    'c'.to_i?     # => nil
    '1'.to_i?(16) # => 1
    'a'.to_i?(16) # => 10
    'f'.to_i?(16) # => 15
    'z'.to_i?(16) # => nil

def to_s(io : IO) : Nil #

Appends this char to the given `IO`.

This appends this char's bytes as encoded by UTF-8 to the given `IO`.

def to_s : String #

Returns this char as a string containing this char as a single character.

    'a'.to_s # => "a"
    'あ'.to_s # => "あ"

def to_u128(base : Int = 10) #

See also: `#to_i`.

def to_u128?(base : Int = 10) #

See also: `#to_i?`.

def to_u16(base : Int = 10) #

See also: `#to_i`.

def to_u16?(base : Int = 10) #

See also: `#to_i?`.

def to_u32(base : Int = 10) #

See also: `#to_i`.

def to_u32?(base : Int = 10) #

See also: `#to_i?`.

def to_u64(base : Int = 10) #

See also: `#to_i`.

def to_u64?(base : Int = 10) #

See also: `#to_i?`.

def to_u8(base : Int = 10) #

See also: `#to_i`.

def to_u8?(base : Int = 10) #

See also: `#to_i?`.

def unicode_escape(io : IO) : Nil #

Returns the Unicode escape sequence representing this character.

The codepoints are expressed as hexadecimal digits with uppercase letters. Unicode escapes always use the four digit style for codepoints `U+FFFF` and lower, adding leading zeros when necessary. Higher codepoints have their digits wrapped in curly braces and no leading zeros.

    'a'.unicode_escape      # => "\\u0061"
    '\t'.unicode_escape     # => "\\u0009"
    'あ'.unicode_escape      # => "\\u3042"
    '\u0012'.unicode_escape # => "\\u0012"
    '😀'.unicode_escape      # => "\\u{1F600}"

def unicode_escape : String #

Returns the Unicode escape sequence representing this character.

The codepoints are expressed as hexadecimal digits with uppercase letters. Unicode escapes always use the four digit style for codepoints `U+FFFF` and lower, adding leading zeros when necessary. Higher codepoints have their digits wrapped in curly braces and no leading zeros.

    'a'.unicode_escape      # => "\\u0061"
    '\t'.unicode_escape     # => "\\u0009"
    'あ'.unicode_escape      # => "\\u3042"
    '\u0012'.unicode_escape # => "\\u0012"
    '😀'.unicode_escape      # => "\\u{1F600}"

def upcase(io : IO, options : Unicode::CaseOptions = :none) : Nil #

Writes the upcase equivalent of this char to the given io.

This method takes into account the possibility that an upcase version of a char might result in multiple chars, like for 'ﬄ', which results in 'F', 'F' and 'L'.

    'z'.upcase(STDOUT) # prints "Z"
    'ﬄ'.upcase(STDOUT) # prints "FFL"

def upcase(options : Unicode::CaseOptions = :none) : Char #

Returns the upcase equivalent of this char.

Note that this only works for characters whose upcase equivalent yields a single codepoint. There are a few characters, like 'ﬄ', than when upcased result in multiple characters (in this case: 'F', 'F', 'L').

For more correct behavior see the overloads that receive a block or an `IO`.

    'z'.upcase # => 'Z'
    'X'.upcase # => 'X'
    '.'.upcase # => '.'

def upcase(options : Unicode::CaseOptions = :none, &) #

Yields each char for the upcase equivalent of this char.

This method takes into account the possibility that an upcase version of a char might result in multiple chars, like for 'ﬄ', which results in 'F', 'F' and 'L'.

    'z'.upcase { |v| puts v } # prints 'Z'
    'ﬄ'.upcase { |v| puts v } # prints 'F', 'F', 'L'

def uppercase? : Bool #

Returns `true` if this char is an uppercase letter.

    'H'.uppercase? # => true
    'Á'.uppercase? # => true
    'c'.uppercase? # => false
    '.'.uppercase? # => false
    'ǲ'.uppercase? # => false

def whitespace? : Bool #

Returns `true` if this char is a whitespace according to unicode.

    ' '.whitespace?  # => true
    '\t'.whitespace? # => true
    'b'.whitespace?  # => false