# `Unicode.String.Break.Tailoring`
[🔗](https://github.com/elixir-unicode/unicode_string/blob/v2.4.1/lib/unicode/string/break/tailoring.ex#L1)

CLDR's locale tailoring of the segmentation rules.

UAX #14 and UAX #29 define one set of rules for all languages. CLDR carries
per-locale departures from them as locale data, and this module applies the
ones this library supports. Two kinds arise:

* **Break class tailoring**, where a locale gives a character a different
  break class from the one the UCD assigns it. Greek treats U+003B as a
  sentence terminator; Japanese and Chinese treat conditional Japanese
  starters as ideographs rather than non-starters, the tailoring usually
  called CJK *loose* line breaking.

* **Abbreviation suppressions**, where a locale lists abbreviations such as
  "Mr." that end in a full stop without ending a sentence.

Neither is expressible in the rules themselves, so both are applied around a
break engine rather than inside it, and this module is the single home for
that behaviour.

# `classify`

Returns the sentence break class of a codepoint under a locale's tailoring.

### Arguments

* `locale` is a locale atom such as `:en` or `:el`.

* `codepoint` is an integer codepoint.

### Returns

* The sentence break class as an atom, such as `:sterm` or `:lower`.

### Examples

    iex> Unicode.String.Break.Tailoring.classify(:en, ?;)
    :scontinue

    iex> Unicode.String.Break.Tailoring.classify(:el, ?;)
    :sterm

# `suppressed?`

Returns `true` when a segment ends in an abbreviation the locale suppresses
breaking after.

CLDR lists abbreviations such as "Mr." and "Dr." that end in a full stop
without ending a sentence. The rules break after them regardless, so the break
is cancelled afterwards by matching the segment's trailing word against the
locale's suppression set.

Only an ATerm-led break can be suppressed. A segment ending in an STerm is a
sentence end whatever word precedes it, and the check rejects it because the
character before the trailing `Close* Sp* ParaSep?` run is not an ATerm.

### Arguments

* `segment` is the candidate sentence, ending at the break being tested.

* `locale` is a locale atom such as `:en` or `:de`.

* `suppressions` is a `MapSet` of downcased abbreviations, as returned by
  `Unicode.String.Segment.suppressions!/2`.

### Returns

* `true` when the break should be cancelled and the segment extended.

* `false` otherwise.

### Examples

    iex> suppressions = MapSet.new(["mr"])
    iex> Unicode.String.Break.Tailoring.suppressed?("Hello Mr.", :en, suppressions)
    true

    iex> suppressions = MapSet.new(["mr"])
    iex> Unicode.String.Break.Tailoring.suppressed?("Hello Ms.", :en, suppressions)
    false

# `tailor`

Rewrites a locale's tailored characters to standard characters carrying the
break class the locale gives them.

A table-driven engine resolves a character to a symbol with a table fixed at
compile time, so it has nowhere to put a per-locale exception. Rewriting the
tailored characters to standard characters of the class the locale wants has
the same effect on every rule.

Each substitute encodes to the same number of UTF-8 bytes as the character it
replaces, so every byte offset computed over the returned string indexes the
original string and segments are sliced from the original rather than from the
rewritten copy. The rewrite never reaches the caller.

### Arguments

* `string` is the text about to be segmented.

* `locale` is a locale atom such as `:en`, `:el` or `:ja`.

* `break_type` is `:sentence`, `:line`, `:word` or `:grapheme`.

### Returns

* `string` unchanged when the locale has no tailoring for this break type,
  which is the overwhelming majority of cases.

* A string of the same byte length with the tailored characters substituted.

### Examples

    iex> Unicode.String.Break.Tailoring.tailor("γδ; Ε", :en, :sentence)
    "γδ; Ε"

    iex> Unicode.String.Break.Tailoring.tailor("γδ; Ε", :el, :sentence)
    "γδ! Ε"

    iex> Unicode.String.Break.Tailoring.tailor("ぁあ", :en, :line)
    "ぁあ"

    iex> Unicode.String.Break.Tailoring.tailor("ぁあ", :ja, :line)
    "一あ"

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*Consult [api-reference.md](api-reference.md) for complete listing*