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Editorial: Make the Locale object abstract operation algorithms more explicit #1087

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Editorial: Make the Locale object abstract operation algorithms more explicit #1087

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24 changes: 14 additions & 10 deletions spec/locale.html
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Original file line number Diff line number Diff line change
Expand Up @@ -492,8 +492,9 @@ <h1>
</dl>
<emu-alg>
1. Let _baseName_ be GetLocaleBaseName(_locale_).
1. Assert: The first subtag of _baseName_ can be matched by the <code>unicode_language_subtag</code> Unicode locale nonterminal.
1. Return the first subtag of _baseName_.
1. Let _subtags_ be StringSplitToList(_baseName_, *"-"*).
1. Assert: _subtags_[0] is matched by the <code>unicode_language_subtag</code> Unicode locale nonterminal.

@ptomato ptomato Jul 7, 2026

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Note, "subtags has at least one element" is implicit here and in similar language below, but I think that's OK.

@gibson042 gibson042 Jul 7, 2026

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That's actually guaranteed by the final three steps of StringSplitToList.

1. Return _subtags_[0].
</emu-alg>
</emu-clause>

Expand All @@ -507,8 +508,10 @@ <h1>
</dl>
<emu-alg>
1. Let _baseName_ be GetLocaleBaseName(_locale_).
1. Assert: _baseName_ contains at most one subtag that can be matched by the <code>unicode_script_subtag</code> Unicode locale nonterminal.
1. If _baseName_ contains a subtag matched by the <code>unicode_script_subtag</code> Unicode locale nonterminal, return that subtag.
1. NOTE: A <code>unicode_script_subtag</code> subtag is only valid immediately after an initial <code>unicode_language_subtag</code> subtag. In that position, it cannot be confused with any other valid subtag because all their productions are disjoint.
1. Let _subtags_ be StringSplitToList(_baseName_, *"-"*).
1. Assert: _subtags_[0] is matched by the <code>unicode_language_subtag</code> Unicode locale nonterminal.
1. If _subtags_ has at least 2 elements and _subtags_[1] is matched by the <code>unicode_script_subtag</code> Unicode locale nonterminal, return _subtags_[1].
1. Return *undefined*.
</emu-alg>
</emu-clause>
Expand All @@ -523,11 +526,11 @@ <h1>
</dl>
<emu-alg>
1. Let _baseName_ be GetLocaleBaseName(_locale_).
1. NOTE: A <code>unicode_region_subtag</code> subtag is only valid immediately after an initial <code>unicode_language_subtag</code> subtag, optionally with a single <code>unicode_script_subtag</code> subtag between them. In that position, <code>unicode_region_subtag</code> cannot be confused with any other valid subtag because all their productions are disjoint.
1. Assert: The first subtag of _baseName_ can be matched by the <code>unicode_language_subtag</code> Unicode locale nonterminal.
1. Let _baseNameTail_ be the suffix of _baseName_ following the first subtag.
1. Assert: _baseNameTail_ contains at most one subtag that can be matched by the <code>unicode_region_subtag</code> Unicode locale nonterminal.
1. If _baseNameTail_ contains a subtag matched by the <code>unicode_region_subtag</code> Unicode locale nonterminal, return that subtag.
1. NOTE: A <code>unicode_region_subtag</code> subtag is only valid immediately after an initial <code>unicode_language_subtag</code> subtag, optionally with a single <code>unicode_script_subtag</code> subtag between them. In that position, it cannot be confused with any other valid subtag because all their productions are disjoint.
1. Let _subtags_ be StringSplitToList(_baseName_, *"-"*).
1. Assert: _subtags_[0] is matched by the <code>unicode_language_subtag</code> Unicode locale nonterminal.
1. If _subtags_ has at least 2 elements and _subtags_[1] is matched by the <code>unicode_region_subtag</code> Unicode locale nonterminal, return _subtags_[1].
1. If _subtags_ has at least 3 elementss and _subtags_[2] is matched by the <code>unicode_region_subtag</code> Unicode locale nonterminal, return _subtags_[2].
1. Return *undefined*.
</emu-alg>
</emu-clause>
Expand All @@ -542,8 +545,9 @@ <h1>
</dl>
<emu-alg>
1. Let _baseName_ be GetLocaleBaseName(_locale_).
1. NOTE: Each subtag in _baseName_ that is preceded by *"-"* is either a <code>unicode_script_subtag</code>, <code>unicode_region_subtag</code>, or <code>unicode_variant_subtag</code>, but any <emu-not-ref>substring</emu-not-ref> matched by <code>unicode_variant_subtag</code> is strictly longer than any prefix thereof which could also be matched by one of the other productions.
1. NOTE: Each non-initial subtag in _baseName_ is either a <code>unicode_script_subtag</code>, <code>unicode_region_subtag</code>, or <code>unicode_variant_subtag</code>, whose productions are all mutually disjoint.
1. Let _subtags_ be StringSplitToList(_baseName_, *"-"*).
1. Assert: _subtags_[0] is matched by the <code>unicode_language_subtag</code> Unicode locale nonterminal.
1. Let _dashIndex_ be the length of _subtags_[0].
1. Remove the first element from _subtags_.
1. For each String _subtag_ of _subtags_, do
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