# `Unicode.String.Case.Mapping.Greek`
[🔗](https://github.com/elixir-unicode/unicode_string/blob/v2.1.0/lib/unicode/case/greek_upper.ex#L1)

Implements the special upper casing rules for
for the Greek language.

# `upcase`

This implementation currently implements the `el-Upper` transform
from CLDR.

### CLDR algorithm

According to CLDR all accents on all characters are are omitted when
upcasing.

  Remove 0301 following Greek, with possible intervening 0308 marks.
  ::NFD();
  For uppercasing (not titlecasing!) remove all greek accents from greek letters.
  This is done in two groups, to account for canonical ordering.
  [:Greek:] [^[:ccc=Not_Reordered:][:ccc=Above:]]*? { [̓̔́̀̆͂̈̄] → ;
  [:Greek:] [^[:ccc=Not_Reordered:][:ccc=Iota_Subscript:]]*? { ͅ → ;
  ::NFC();

That transform basically says remove all accents except a
subscripted iota. It doesn't handle dipthongs correctly.

### Mozilla algorithm

Mozilla has a thread on a [bug report](https://bugzilla.mozilla.org/show_bug.cgi?id=307039)
that:

>  Greek accented letters should be converted to the respective non-accented uppercase
>  letters. The required conversions are the following (in Unicode):
>
>  ά -> Α
>  έ -> Ε
>  ή -> Η
>  ί -> Ι
>  ΐ -> Ϊ
>  ό -> Ο
>  ύ -> Υ
>  ΰ -> Ϋ
>  ώ -> Ω
>
>  Also diphthongs (two-vowel constructs) should be converted as follows, when the
>  first vowel is accented:
>
>  άι -> ΑΪ
>  έι -> ΕΪ
>  όι -> ΟΪ
>  ύι -> ΥΪ
>  άυ -> ΑΫ
>  έυ -> ΕΫ
>  ήυ -> ΗΫ
>  όυ -> ΟΫ

That thread seems to align with current-day [Mozilla](https://developer.mozilla.org/en-US/docs/Web/CSS/text-transform)
which says the rules are:

> In Greek (el), vowels lose their accent when the whole word is in
> uppercase (ά/Α), except for the disjunctive eta (ή/Ή). Also, diphthongs
> with an accent on the first vowel lose the accent and gain a diaeresis
> on the second vowel (άι/ΑΪ).

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