silk.text.char.

When to use#

Use fromU32 to make a char from an integer code point, and toU32 to get the code point. Use the comparison operators in ordinary expressions. Use the named comparison functions when a comparison must be a function value.

Details#

A char is one Unicode scalar value: a code point from 0 to 0x10FFFF that is not a surrogate. Comparisons use the numeric code point. They do not use locale rules, normalization, grapheme clusters, or UTF-8 bytes. These functions do not allocate and have no effects.

Gotchas#

fromU32 returns None for the surrogates 0xD800 to 0xDFFF and for values more than 0x10FFFF. It does not truncate and does not trap.

Examples#

Validate a Unicode scalar integer#

import silk.text.char
import silk.core.option { Option }

pub fn main() -> i32 {
  let scalar = char.fromU32(0x2603)
  let value = move scalar |> Option<char>.unwrapOr('?')
  if char.toU32(value) != 0x2603 {
    return 1
  }
  let surrogate = char.fromU32(0xD800)
  let replacement = move surrogate |> Option<char>.unwrapOr('?')
  if replacement != '?' {
    return 1
  }
  return 0
}

Import as char with import silk.text.char.

Public declarations: 8.

fromU32#

pub fn fromU32(value: u32) -> Option<char>

Returns the char with code point value, or None if value is not a Unicode scalar value.

When to use#

Use fromU32 to check a code point from untrusted input, such as a decoded escape sequence.

Details#

The result is None for the surrogates 0xD800 to 0xDFFF and for values more than 0x10FFFF. For each other value, the result is present.

toU32#

pub fn toU32(value: char) -> u32

Returns the code point of value. The result is at most 0x10FFFF and is never a surrogate.

equals#

pub fn equals(left: char, right: char) -> bool

Returns true if left and right have the same code point. This function has the same result as left == right.

notEquals#

pub fn notEquals(left: char, right: char) -> bool

Returns true if left and right have different code points. This function has the same result as left != right.

lessThan#

pub fn lessThan(left: char, right: char) -> bool

Returns true if the code point of left is less than the code point of right.

lessOrEqual#

pub fn lessOrEqual(left: char, right: char) -> bool

Returns true if the code point of left is less than or equal to the code point of right.

greaterThan#

pub fn greaterThan(left: char, right: char) -> bool

Returns true if the code point of left is more than the code point of right.

greaterOrEqual#

pub fn greaterOrEqual(left: char, right: char) -> bool

Returns true if the code point of left is more than or equal to the code point of right.

Category: Text.

Profiles: aarch64-apple-darwin, aarch64-unknown-linux-gnu, aarch64-unknown-linux-gnu-no-libc, x86_64-unknown-linux-gnu, x86_64-unknown-linux-gnu-no-libc, wasm32-unknown-unknown, wasm32-wasip1, wasm32-wasip2.