struct Char

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 at most three digits to denote a code point written in octal:

'\101' # == 'A'
'\123' # == 'S'
'\12'  # == '\n'
'\1'   # code point 1

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'

Included Modules

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

ZERO = '\u{0}'

The character representing the end of a C string.

Instance Method Summary

Instance methods inherited from module Comparable({"T", T})

<(other : T) <, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) >, >=(other : T) >=

Instance methods inherited from struct Value

==(other) ==, dup dup

Instance methods inherited from class Object

!=(other) !=, !~(other) !~, ==(other) ==, ===(other)
===(other : YAML::Any)
===(other : JSON::Any) ===, =~(other) =~, class class, crystal_type_id crystal_type_id, dup dup, hash hash, inspect(io : IO)
inspect inspect, itself itself, not_nil! not_nil!, tap(&block) tap, to_json to_json, to_pretty_json(indent : String = " ")
to_pretty_json(io : IO, indent : String = " ") to_pretty_json, to_s
to_s(io : IO) to_s, to_yaml
to_yaml(io : IO) to_yaml, try(&block) try

Class methods inherited from class Object

==(other : Class) ==, ===(other) ===, cast(other) : self cast, clone clone, dup dup, from_json(string_or_io) : self
from_json(string_or_io, root : String) : self from_json, from_yaml(string : String) : self from_yaml, hash hash, inspect(io) inspect, name : String name, nilable? nilable?, to_s(io) to_s, |(other : U.class) |

Instance Method Detail

def !=(other : Char) : Bool #

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


[View source]
def +(str : String) #

Concatenates this char and string.

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

[View source]
def -(other : Char) #

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

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

[View source]
def <(other : Char) : Bool #

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


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def <=(other : Char) : Bool #

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


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def <=>(other : Char) #

Implements the comparison operator.

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

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def ==(other : Char) : Bool #

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


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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

[View source]
def >(other : Char) : Bool #

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


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def >=(other : Char) : Bool #

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


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def alpha? #

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

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

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def alphanumeric? #

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

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

[View source]
def ascii? #

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


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def bytes #

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

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

[View source]
def bytesize #

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

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

[View source]
def clone #

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def control? #

Returns true if this char is an ASCII control character.

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

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

[View source]
def digit?(base : Int = 10) #

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

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

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

[View source]
def downcase #

Returns the ASCII downcase equivalent of this char.

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

[View source]
def dump #

Returns this char as a string that contains a char literal as written in Crystal, with characters with a codepoint greater than 0x79 written as \u{...}.

'a'.dump      # => "'a'"
'\t'.dump     # => "'\t'"
'あ'.dump      # => "'\u{3042}'"
'\u0012'.dump # => "'\u{12}'"

[View source]
def dump(io) #

Appends this char as a string that contains a char literal to the given IO.

See #dump.


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def each_byte(&block) #

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

[View source]
def hash #

Returns this char's codepoint.


[View source]
def hex? #

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

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

[View source]
def in_set?(*sets : String) #

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 the end of a a 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

[View source]
def inspect(io) #

Appends this char as a string that contains a char literal to the given IO.

See #inspect.


[View source]
def inspect #

Returns this char as a string that contains a char literal.

'a'.inspect      # => "'a'"
'\t'.inspect     # => "'\t'"
'あ'.inspect      # => "'あ'"
'\u0012'.inspect # => "'\u{12}'"

[View source]
def lowercase? #

Returns true if this char is a lowercase ASCII letter.

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

[View source]
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

[View source]
def pred #

Returns a Char that is one codepoint smaller than this char's codepoint.

'b'.pred # => 'a'
'ぃ'.pred # => 'あ'

[View source]
def succ #

Returns a Char that is one codepoint bigger than this char's codepoint.

'a'.succ # => 'b'
'あ'.succ # => 'ぃ'

This method allows creating a Range of chars.


[View source]
def to_f #

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

'1'.to_i # => 1.0
'8'.to_i # => 8.0
'c'.to_i # => ArgumentError

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def to_f32 #

See #to_f


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def to_f32? #

See #to_f?


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def to_f64 #

Same as #to_f


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def to_f64? #

Same as #to_f?


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def to_f? #

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

'1'.to_i # => 1.0
'8'.to_i # => 8.0
'c'.to_i # => ArgumentError

[View source]
def to_i(base : Int = 10) #

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

[View source]
def to_i16(base : Int = 10) #

See #to_i


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def to_i16?(base : Int = 10) #

See #to_i?


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def to_i32(base : Int = 10) #

Same as #to_i


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def to_i32?(base : Int = 10) #

Same as #to_i?


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def to_i64(base : Int = 10) #

See #to_i


[View source]
def to_i64?(base : Int = 10) #

See #to_i?


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def to_i8(base : Int = 10) #

See #to_i


[View source]
def to_i8?(base : Int = 10) #

See #to_i?


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def to_i?(base : Int = 10) #

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

[View source]
def to_s(io : IO) #

Appends this char to the given IO.

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


[View source]
def to_s #

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

'a'.to_s # => "a"
'あ'.to_s # => "あ"

[View source]
def to_u16(base : Int = 10) #

See #to_i


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def to_u16?(base : Int = 10) #

See #to_i?


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def to_u32(base : Int = 10) #

See #to_i


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def to_u32?(base : Int = 10) #

See #to_i?


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def to_u64(base : Int = 10) #

See #to_i


[View source]
def to_u64?(base : Int = 10) #

See #to_i?


[View source]
def to_u8(base : Int = 10) #

See #to_i


[View source]
def to_u8?(base : Int = 10) #

See #to_i?


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def upcase #

Returns the ASCII upcase equivalent of this char.

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

[View source]
def uppercase? #

Returns true if this char is an uppercase ASCII letter.

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

[View source]
def whitespace? #

Returns true if this char is an ASCII whitespace.

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

[View source]