W3cubDocs

/Crystal 0.31

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 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.

REPLACEMENT = '�'

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

ZERO = '\u{0}'

The character representing the end of a C string.

Instance Method Summary

Instance Method Detail

def !=(other : Char) : BoolSource

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

def +(str : String)Source

Concatenates this char and string.

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

def +(other : Int) : CharSource

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

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

def -(other : Char)Source

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

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

def -(other : Int) : CharSource

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

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

def <(other : Char) : BoolSource

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

def <=(other : Char) : BoolSource

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

def <=>(other : Char)Source

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) : BoolSource

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

def ===(byte : Int)Source

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) : BoolSource

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

def >=(other : Char) : BoolSource

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

def alphanumeric?Source

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

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

def ascii?Source

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

def ascii_alphanumeric?Source

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?Source

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

def ascii_letter?Source

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?Source

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)Source

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

def ascii_uppercase?Source

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?Source

Returns true if this char is an ASCII whitespace.

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

def bytesSource

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

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

def bytesizeSource

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

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

def cloneSource

def control?Source

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

def downcase(options = Unicode::CaseOptions::None)Source

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 # => '.'

def downcase(options = Unicode::CaseOptions::None, &block)Source

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.

def dumpSource

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}'"

def dump(io)Source

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

See also: #dump.

def each_byte(&block) : NilSource

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)Source

def hex?Source

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)Source

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 : StringSource

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

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

def inspect(io : IO) : NilSource

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

See also: #inspect.

def letter?Source

Returns true if this char is a letter.

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

def lowercase?Source

Returns true if this char is a lowercase letter.

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

def mark?Source

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

def number?Source

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

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

def ord : Int32Source

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 predSource

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

'b'.pred # => 'a'
'ぃ'.pred # => 'あ'

def succSource

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.

def to_fSource

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_f32Source

See also: #to_f.

def to_f32?Source

See also: #to_f?.

def to_f64Source

Same as #to_f.

def to_f64?Source

Same as #to_f?.

def to_f?Source

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) : Int32Source

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_i16(base : Int = 10)Source

See also: #to_i.

def to_i16?(base : Int = 10)Source

See also: #to_i?.

def to_i32(base : Int = 10) : Int32Source

Same as #to_i.

def to_i32?(base : Int = 10) : Int32?Source

Same as #to_i?.

def to_i64(base : Int = 10)Source

See also: #to_i.

def to_i64?(base : Int = 10)Source

See also: #to_i?.

def to_i8(base : Int = 10)Source

See also: #to_i.

def to_i8?(base : Int = 10)Source

See also: #to_i?.

def to_i?(base : Int = 10) : Int32?Source

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 : StringSource

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

'a'.to_s # => "a"
'あ'.to_s # => "あ"

def to_s(io : IO) : NilSource

Appends this char to the given IO.

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

def to_u16(base : Int = 10)Source

See also: #to_i.

def to_u16?(base : Int = 10)Source

See also: #to_i?.

def to_u32(base : Int = 10)Source

See also: #to_i.

def to_u32?(base : Int = 10)Source

See also: #to_i?.

def to_u64(base : Int = 10)Source

See also: #to_i.

def to_u64?(base : Int = 10)Source

See also: #to_i?.

def to_u8(base : Int = 10)Source

See also: #to_i.

def to_u8?(base : Int = 10)Source

See also: #to_i?.

def upcase(options = Unicode::CaseOptions::None, &block)Source

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 upcase(options = Unicode::CaseOptions::None)Source

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 # => '.'

def uppercase?Source

Returns true if this char is an uppercase letter.

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

def whitespace?Source

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

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

© 2012–2019 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/0.31.1/Char.html