Skip to main content

core/Char

Module for working with Characters (Unicode code points).

Characters in Motoko represent Unicode code points in the range 0 to 0x10FFFF, excluding the surrogate code points (0xD800 through 0xDFFF).

Import from the core library to use this module.

import Char "mo:core/Char";

Some built in features not listed in this module:

  • You can create a Char literal using single quotes, e.g. 'A', '1', '漢'
  • You can compare characters using <, <=, ==, !=, >=, > operators
  • You can convert a single-character Text to a Char using :Char type annotation

For example:

let char : Char = 'A';
let unicodeChar = '漢';
let digit = '7';
assert Char.isDigit(digit);
assert Char.toText(char) == "A";

Type Char​

type Char = Prim.Types.Char

Characters represented as Unicode code points.

Function toNat32​

func toNat32(char : Char) : Nat32

Convert character char to a word containing its Unicode scalar value.

Example:

let char = 'A';
let unicode = Char.toNat32(char);
assert unicode == 65;

Function fromNat32​

func fromNat32(nat32 : Nat32) : Char

Convert w to a character. Traps if w is not a valid Unicode scalar value. Value w is valid if, and only if, w < 0xD800 or (0xE000 <= w and w <= 0x10FFFF).

Example:

let unicode : Nat32 = 65;
let char = Char.fromNat32(unicode);
assert char == 'A';

Function toText​

func toText(char : Char) : Text

Convert character char to single character text.

Example:

let char = '漢';
let text = Char.toText(char);
assert text == "漢";

Function isDigit​

func isDigit(char : Char) : Bool

Returns true when char is a decimal digit between 0 and 9, otherwise false.

Example:

assert Char.isDigit('5');
assert not Char.isDigit('A');

Function isWhitespace​

func isWhitespace(char : Char) : Bool

Returns whether char is a whitespace character. Whitespace characters include space, tab, newline, etc.

Example:

assert Char.isWhitespace(' ');
assert Char.isWhitespace('\n');
assert not Char.isWhitespace('A');

Function isLower​

func isLower(char : Char) : Bool

Returns whether char is a lowercase character.

Example:

assert Char.isLower('a');
assert not Char.isLower('A');

Function isUpper​

func isUpper(char : Char) : Bool

Returns whether char is an uppercase character.

Example:

assert Char.isUpper('A');
assert not Char.isUpper('a');

Function isAlphabetic​

func isAlphabetic(char : Char) : Bool

Returns whether char is an alphabetic character.

Example:

assert Char.isAlphabetic('A');
assert Char.isAlphabetic('漢');
assert not Char.isAlphabetic('1');

Function equal​

func equal(a : Char, b : Char) : Bool

Returns a == b.

Example:

assert Char.equal('A', 'A');
assert not Char.equal('A', 'B');

Note: The reason why this function is defined in this library (in addition to the existing == operator) is so that you can use it as a function value to pass to a higher order function.

Function notEqual​

func notEqual(a : Char, b : Char) : Bool

Returns a != b.

Example:

assert Char.notEqual('A', 'B');
assert not Char.notEqual('A', 'A');

Note: The reason why this function is defined in this library (in addition to the existing != operator) is so that you can use it as a function value to pass to a higher order function.

Function less​

func less(a : Char, b : Char) : Bool

Returns a < b.

Example:

assert Char.less('A', 'B');
assert not Char.less('B', 'A');

Note: The reason why this function is defined in this library (in addition to the existing < operator) is so that you can use it as a function value to pass to a higher order function.

Function lessOrEqual​

func lessOrEqual(a : Char, b : Char) : Bool

Returns a <= b.

Example:

assert Char.lessOrEqual('A', 'A');
assert Char.lessOrEqual('A', 'B');
assert not Char.lessOrEqual('B', 'A');

Note: The reason why this function is defined in this library (in addition to the existing <= operator) is so that you can use it as a function value to pass to a higher order function.

Function greater​

func greater(a : Char, b : Char) : Bool

Returns a > b.

Example:

assert Char.greater('B', 'A');
assert not Char.greater('A', 'B');

Note: The reason why this function is defined in this library (in addition to the existing > operator) is so that you can use it as a function value to pass to a higher order function.

Function greaterOrEqual​

func greaterOrEqual(a : Char, b : Char) : Bool

Returns a >= b.

Example:

assert Char.greaterOrEqual('B', 'A');
assert Char.greaterOrEqual('A', 'A');
assert not Char.greaterOrEqual('A', 'B');

Note: The reason why this function is defined in this library (in addition to the existing >= operator) is so that you can use it as a function value to pass to a higher order function.

Function compare​

func compare(a : Char, b : Char) : {#less; #equal; #greater}

Returns the order of a and b.

Example:

assert Char.compare('A', 'B') == #less;
assert Char.compare('B', 'A') == #greater;
assert Char.compare('A', 'A') == #equal;