struct Char
inherits Value
¶
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'
Included modules
Comparable
Steppable
Constants¶
MAX = 1114111.unsafe_chr
¶
1114111.unsafe_chr
The maximum character.
MAX_CODEPOINT = 1114111
¶
1114111
The maximum valid codepoint for a character.
REPLACEMENT = '�'
¶
'�'
The replacement character, used on invalid UTF-8 byte sequences.
ZERO = '\u{0}'
¶
'\u{0}'
The character representing the end of a C string.
Methods¶
#!=(other : Char) : Bool
¶
(other : Char) : Bool
Returns true if self's codepoint is not equal to other's codepoint.
#+(other : Int) : Char
¶
(other : Int) : Char
Returns a char that has this char's codepoint plus other.
'a' + 1 # => 'b'
'a' + 2 # => 'c'
#-(other : Char)
¶
(other : Char)
Returns the difference of the codepoint values of this char and other.
'a' - 'a' # => 0
'b' - 'a' # => 1
'c' - 'a' # => 2
#-(other : Int) : Char
¶
(other : Int) : Char
Returns a char that has this char's codepoint minus other.
'c' - 1 # => 'b'
'c' - 2 # => 'a'
#<(other : Char) : Bool
¶
(other : Char) : Bool
Returns true if self's codepoint is less than other's codepoint.
#<=(other : Char) : Bool
¶
(other : Char) : Bool
Returns true if self's codepoint is less than or equal to other's codepoint.
#<=>(other : Char)
¶
(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
#==(other : Char) : Bool
¶
(other : Char) : Bool
Returns true if self's codepoint is equal to other's codepoint.
#===(byte : Int)
¶
(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
#>(other : Char) : Bool
¶
(other : Char) : Bool
Returns true if self's codepoint is greater than other's codepoint.
#>=(other : Char) : Bool
¶
(other : Char) : Bool
Returns true if self's codepoint is greater than or equal to other's codepoint.
#alphanumeric?
¶
Returns true if this char is a letter or a number according to unicode.
'c'.alphanumeric? # => true
'8'.alphanumeric? # => true
'.'.alphanumeric? # => false
#ascii_alphanumeric?
¶
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
#ascii_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
#ascii_letter?
¶
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
#ascii_lowercase?
¶
Returns true if this char is a lowercase ASCII letter.
'c'.ascii_lowercase? # => true
'ç'.lowercase? # => true
'G'.ascii_lowercase? # => false
'.'.ascii_lowercase? # => false
#ascii_number?(base : Int = 10)
¶
(base : Int = 10)
Returns true if this char is an ASCII number 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'.ascii_number? # => true
'z'.ascii_number? # => false
'z'.ascii_number?(36) # => true
#ascii_uppercase?
¶
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
#ascii_whitespace?
¶
Returns true if this char is an ASCII whitespace.
' '.ascii_whitespace? # => true
'\t'.ascii_whitespace? # => true
'b'.ascii_whitespace? # => false
#bytes
¶
Returns this char bytes as encoded by UTF-8, as an Array(UInt8).
'a'.bytes # => [97]
'あ'.bytes # => [227, 129, 130]
#bytesize
¶
Returns the number of UTF-8 bytes in this char.
'a'.bytesize # => 1
'好'.bytesize # => 3
#downcase(options = Unicode::CaseOptions::None
¶
(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.
#downcase(options = Unicode::CaseOptions::None)
¶
(options = Unicode::CaseOptions::None)
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 a more correct method see the method that receives a block.
'Z'.downcase # => 'z'
'x'.downcase # => 'x'
'.'.downcase # => '.'
#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}'"
#dump(io)
¶
View source
(io)
#each_byte(&) : Nil
¶
(&) : 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
#hex?
¶
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
#in_set?(*sets : String)
¶
(*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 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
#inspect : String
¶
: String
Returns this char as a string that contains a char literal.
'a'.inspect # => "'a'"
'\t'.inspect # => "'\\t'"
'あ'.inspect # => "'あ'"
'\u0012'.inspect # => "'\\u{12}'"
#inspect(io : IO) : Nil
¶
View source
(io : IO) : Nil
#letter?
¶
Returns true if this char is a letter.
'c'.letter? # => true
'á'.letter? # => true
'8'.letter? # => false
#lowercase?
¶
Returns true if this char is a lowercase letter.
'c'.lowercase? # => true
'ç'.lowercase? # => true
'G'.lowercase? # => false
'.'.lowercase? # => false
#number?
¶
Returns true if this char is a number according to unicode.
'1'.number? # => true
'a'.number? # => false
#ord : Int32
¶
: 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
#pred
¶
Returns a Char that is one codepoint smaller than this char's codepoint.
'b'.pred # => 'a'
'ぃ'.pred # => 'あ'
#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.
#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_f # => 1.0
'8'.to_f # => 8.0
'c'.to_f # raises ArgumentError
#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_f? # => 1.0
'8'.to_f? # => 8.0
'c'.to_f? # => nil
#to_i(base : Int = 10) : Int32
¶
(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
#to_i?(base : Int = 10) : Int32?
¶
(base : Int = 10) : Int32?
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
#to_s : String
¶
: String
Returns this char as a string containing this char as a single character.
'a'.to_s # => "a"
'あ'.to_s # => "あ"
#to_s(io : IO) : Nil
¶
(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.
#upcase(options = Unicode::CaseOptions::None
¶
(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'
#upcase(options = Unicode::CaseOptions::None)
¶
(options = Unicode::CaseOptions::None)
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 a more correct method see the method that receives a block.
'z'.upcase # => 'Z'
'X'.upcase # => 'X'
'.'.upcase # => '.'
#uppercase?
¶
Returns true if this char is an uppercase letter.
'H'.uppercase? # => true
'Á'.uppercase? # => true
'c'.uppercase? # => false
'.'.uppercase? # => false
#whitespace?
¶
Returns true if this char is a whitespace according to unicode.
' '.whitespace? # => true
'\t'.whitespace? # => true
'b'.whitespace? # => false