Module

std.text.unicode

Enums

public enum GraphemeBreakProperty

One of the UAX #29 Grapheme_Cluster_Break property values.

Returned by graphemeBreakProperty(c:) and consumed by shouldBreakBetween(...). Variant names match the Unicode property labels — see UAX #29 for the precise definitions and the boundary rules (GB1–GB999) that consume them.

Representation

A 14-state tag enum (no payload). ordinal() gives the numeric encoding used by the stage-2 lookup table.

Functions

public func caseFold(Char) -> Char

Single-codepoint case fold for c. Use when comparing characters case-insensitively: caseFold(a) == caseFold(b) is the canonical per-character equality test.

For codepoints whose Unicode fold is multi-codepoint (e.g. ß → ss), this returns only the first folded codepoint — see caseFoldExpansion for the full sequence.

Examples

caseFold('A')                       // 'a'
caseFold('İ')                       // 'i' — see caseFoldExpansion for "i\u{307}"
caseFold('a') == caseFold('A')      // true

public func caseFoldExpansion(Char) -> String

Full Unicode case fold of c as a String. Returns "" when c has no multi-codepoint fold — pair with hasCaseFoldExpansion, or fall back to caseFold for the single-codepoint form.

Examples

caseFoldExpansion('ß')              // "ss"
caseFoldExpansion('ﬃ')             // "ffi"
caseFoldExpansion('a')              // ""  (no expansion; caseFold('a') == 'a')

public func graphemeBreakProperty(Char) -> GraphemeBreakProperty

Looks up the UAX #29 Grapheme_Cluster_Break property for c.

O(1) — two array indexings into the trie. Codepoints above U+10FFFF (which are not valid Unicode scalars) yield .Other.

Examples

graphemeBreakProperty('a')                  // .Other
graphemeBreakProperty('\r')                 // .CR
graphemeBreakProperty('\u{200D}')           // .ZWJ

public func hasCaseFoldExpansion(Char) -> Bool

true iff folding c produces more than one codepoint. Linear scan over FOLD_EXPANSIONS (~100 entries) — fine per-character but quadratic if applied across a large set.

public func hasLowercaseExpansion(Char) -> Bool

true iff lowercasing c produces more than one codepoint. Same scan caveats as hasUppercaseExpansion.

public func hasTitlecaseExpansion(Char) -> Bool

true iff titlecasing c produces more than one codepoint.

public func hasUppercaseExpansion(Char) -> Bool

true iff uppercasing c produces more than one codepoint. Linear scan over UPPER_EXPANSIONS (~100 entries); fine for per-character calls in normal text but quadratic if applied to a large codepoint set.

public func lowercaseExpansion(Char) -> String

Full Unicode lowercase expansion for c. Empty string when no multi-codepoint expansion applies — see uppercaseExpansion for the same shape.

public func shouldBreakBetween(GraphemeBreakProperty, GraphemeBreakProperty, Bool, Bool) -> Bool

Decides whether a grapheme cluster boundary lies between two adjacent codepoints with the given break properties.

Implements the UAX #29 boundary rules GB3–GB13/GB999. The caller must thread two scalar bits across calls to capture rules that look further back than one codepoint:

prevPrevWasRI: was the codepoint before prev a Regional_Indicator? Needed to keep regional-indicator pairs together while still breaking between successive pairs (GB12/13).
prevWasZWJ: was the codepoint before prev a ZWJ? Needed for the simplified emoji ZWJ-sequence rule (GB11).

Returns true to break (start a new cluster at curr), false to keep prev and curr in the same cluster.

public func titlecaseExpansion(Char) -> String

Full Unicode titlecase expansion for c. Empty string when no multi-codepoint expansion applies.

public func toLowercase(Char) -> Char

Single-codepoint lowercase mapping for c. Same caveats as toUppercase: codepoints with multi-char lowercase forms return only the first codepoint — see lowercaseExpansion.

public func toTitlecase(Char) -> Char

Single-codepoint titlecase mapping for c. Differs from toUppercase only for the codepoints (mostly Greek/Croatian digraphs) where Unicode defines a distinct "Title" form. Multi-char expansions live in titlecaseExpansion.

public func toUppercase(Char) -> Char

Single-codepoint uppercase mapping for c. Falls back to c for characters with no mapping and for codepoints above U+10FFFF.

For characters whose Unicode uppercase form expands to multiple codepoints (e.g. ß → SS, ﬁ → FI), this returns only the first codepoint of the expansion. Use hasUppercaseExpansion(c:) to detect the multi-char case and uppercaseExpansion(c:) to retrieve the full String.

Examples

toUppercase('a')           // 'A'
toUppercase('ß')           // 'S' — see uppercaseExpansion for "SS"
toUppercase('1')           // '1' — no mapping

public func uppercaseExpansion(Char) -> String

Full Unicode uppercase expansion for c as a String. Returns the empty string when c has no multi-codepoint expansion — pair with hasUppercaseExpansion (or call toUppercase instead) to avoid the scan when you only need the single-codepoint form.

Examples

uppercaseExpansion('ß')          // "SS"
uppercaseExpansion('ﬁ')          // "FI"
uppercaseExpansion('a')          // ""  (use toUppercase for 'A')

field

public let unicodeVersion: String

Unicode version these tables track. Bump alongside the regeneration of the underlying data/*.bin files.