Char

The Char type represents a single Unicode character (code point). Create character values from one-character strings or Unicode code points.

Literals

Creating Characters

Char

Create character values from one-character strings or Unicode code points.

letter = Char.from-string "a" |> Option.unwrap
digit = Char.from-string "5" |> Option.unwrap
symbol = Char.from-code-point 42 |> Option.unwrap

println letter
# => 'a'

Conversions

Char.from-code-point

Int -> Option Char

Creates a character from a Unicode code point. Returns None for invalid code points.

println (Char.from-code-point 65)
# => Some('A')

println (Char.from-code-point 128054)
# => Some('🐶')

println (Char.from-code-point -1)
# => None

Char.to-code-point

Char -> Int

Returns the Unicode code point of a character.

letter = Char.from-string "A" |> Option.unwrap
dog = Char.from-code-point 128054 |> Option.unwrap

println (Char.to-code-point letter)
# => 65

println (Char.to-code-point dog)
# => 128054

Char.from-string

String -> Option Char

Converts a single-character string to a Char. Returns None if the string is empty or has multiple characters.

println (Char.from-string "a")
# => Some('a')

println (Char.from-string "ab")
# => None

println (Char.from-string "")
# => None

Char.to-string

Char -> String

Converts a character to a single-character string.

letter = Char.from-string "a" |> Option.unwrap
symbol = Char.from-code-point 9733 |> Option.unwrap

println (Char.to-string letter)
# => "a"

println (Char.to-string symbol)
# => "*"

Predicates

Char.is-alpha?

Char -> Bool

Returns true if the character is an alphabetic letter (a-z, A-Z).

a = Char.from-string "a" |> Option.unwrap
z = Char.from-string "Z" |> Option.unwrap
five = Char.from-string "5" |> Option.unwrap

println (Char.is-alpha? a)    # => true
println (Char.is-alpha? z)    # => true
println (Char.is-alpha? five) # => false

Char.is-digit?

Char -> Bool

Returns true if the character is a decimal digit (0-9).

five = Char.from-string "5" |> Option.unwrap
a = Char.from-string "a" |> Option.unwrap

println (Char.is-digit? five) # => true
println (Char.is-digit? a)    # => false

Char.is-alphanumeric?

Char -> Bool

Returns true if the character is alphabetic or a digit.

a = Char.from-string "a" |> Option.unwrap
five = Char.from-string "5" |> Option.unwrap
bang = Char.from-string "!" |> Option.unwrap

println (Char.is-alphanumeric? a)    # => true
println (Char.is-alphanumeric? five) # => true
println (Char.is-alphanumeric? bang) # => false

Char.is-whitespace?

Char -> Bool

Returns true if the character is whitespace (space, tab, newline, etc.).

space = Char.from-string " " |> Option.unwrap
newline = Char.from-code-point 10 |> Option.unwrap
a = Char.from-string "a" |> Option.unwrap

println (Char.is-whitespace? space)   # => true
println (Char.is-whitespace? newline) # => true
println (Char.is-whitespace? a)       # => false

Char.is-uppercase?

Char -> Bool

Returns true if the character is an uppercase letter.

upper = Char.from-string "A" |> Option.unwrap
lower = Char.from-string "a" |> Option.unwrap

println (Char.is-uppercase? upper) # => true
println (Char.is-uppercase? lower) # => false

Char.is-lowercase?

Char -> Bool

Returns true if the character is a lowercase letter.

lower = Char.from-string "a" |> Option.unwrap
upper = Char.from-string "A" |> Option.unwrap

println (Char.is-lowercase? lower) # => true
println (Char.is-lowercase? upper) # => false

Char.is-ascii?

Char -> Bool

Returns true if the character is in the ASCII range (0-127).

a = Char.from-string "a" |> Option.unwrap
dog = Char.from-code-point 128054 |> Option.unwrap

println (Char.is-ascii? a)   # => true
println (Char.is-ascii? dog) # => false

Char.is-control?

Char -> Bool

Returns true if the character is a control character.

newline = Char.from-code-point 10 |> Option.unwrap
a = Char.from-string "a" |> Option.unwrap

println (Char.is-control? newline) # => true
println (Char.is-control? a)       # => false

Char.is-punctuation?

Char -> Bool

Returns true if the character is a punctuation character.

dot = Char.from-string "." |> Option.unwrap
bang = Char.from-string "!" |> Option.unwrap
a = Char.from-string "a" |> Option.unwrap

println (Char.is-punctuation? dot)  # => true
println (Char.is-punctuation? bang) # => true
println (Char.is-punctuation? a)    # => false

Char.is-hex-digit?

Char -> Bool

Returns true if the character is a hexadecimal digit (0-9, a-f, A-F).

a = Char.from-string "a" |> Option.unwrap
f = Char.from-string "F" |> Option.unwrap
g = Char.from-string "g" |> Option.unwrap

println (Char.is-hex-digit? a) # => true
println (Char.is-hex-digit? f) # => true
println (Char.is-hex-digit? g) # => false

Char.is-printable?

Char -> Bool

Returns true if the character is printable (visible when rendered).

a = Char.from-string "a" |> Option.unwrap
space = Char.from-string " " |> Option.unwrap
newline = Char.from-code-point 10 |> Option.unwrap

println (Char.is-printable? a)       # => true
println (Char.is-printable? space)   # => true
println (Char.is-printable? newline) # => false

Case Conversion

Char.to-uppercase

Char -> Char

Converts a character to uppercase. Non-letter characters are returned unchanged.

lower = Char.from-string "a" |> Option.unwrap
upper = Char.from-string "A" |> Option.unwrap
five = Char.from-string "5" |> Option.unwrap

println (Char.to-uppercase lower) # => 'A'
println (Char.to-uppercase upper) # => 'A'
println (Char.to-uppercase five)  # => '5'

Char.to-lowercase

Char -> Char

Converts a character to lowercase. Non-letter characters are returned unchanged.

upper = Char.from-string "A" |> Option.unwrap
lower = Char.from-string "a" |> Option.unwrap
five = Char.from-string "5" |> Option.unwrap

println (Char.to-lowercase upper) # => 'a'
println (Char.to-lowercase lower) # => 'a'
println (Char.to-lowercase five)  # => '5'

Comparison

Char.compare

Char -> Char -> Ordering

Compares two characters by their code points. Returns Less, Equal, or Greater.

a = Char.from-string "a" |> Option.unwrap
b = Char.from-string "b" |> Option.unwrap
c = Char.from-string "c" |> Option.unwrap

println (Char.compare a b) # => Less
println (Char.compare b b) # => Equal
println (Char.compare c a) # => Greater

Working with Strings

Use String.chars to convert a string to a list of characters, and String.from-chars to convert back.

chars = String.chars "hello"
# => ['h', 'e', 'l', 'l', 'o']

upper = chars |>> map Char.to-uppercase |> String.from-chars
# => "HELLO"