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GH-46589: [C++] Fix utf8_is_digit to support full Unicode digit range #46590

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Merged
pitrou merged 2 commits into from
Jun 2, 2025
Merged

GH-46589: [C++] Fix utf8_is_digit to support full Unicode digit range #46590

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7e38020
ARROW-46589: Fixed utf8_is_digit to support full Unicode digit range
iabhi4 May 26, 2025
ce92151
Fix lint
pitrou Jun 2, 2025
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13 changes: 9 additions & 4 deletions cpp/src/arrow/compute/kernels/scalar_string_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1384,10 +1384,15 @@ TYPED_TEST(TestStringKernels, IsDecimalUnicode) {
}

TYPED_TEST(TestStringKernels, IsDigitUnicode) {
// These are digits according to Python, but we don't have the information in
// utf8proc for this
// this->CheckUnary("utf8_is_digit", "[\"²\", \"①\"]", boolean(), "[true,
// true]");
// Tests for digits across various Unicode scripts.
// ٤: Arabic 4, ³: Superscript 3, ५: Devanagari 5, Ⅷ: Roman 8 (not digit),
// １２３: Fullwidth 123.
// '¾' (vulgar fraction) is treated as a digit by utf8proc
this->CheckUnary(
"utf8_is_digit",
R"(["0", "٤", "۵", "३", "१२३", "٣٣", "²", "１２３", "٣٢", "٩", "①", "Ⅷ", "abc" , "⻁", ""])",
boolean(),
R"([true, true, true, true, true, true, true, true, true, true, true, false, false, false, false])");
}

TYPED_TEST(TestStringKernels, IsNumericUnicode) {
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9 changes: 6 additions & 3 deletions cpp/src/arrow/compute/kernels/scalar_string_utf8.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -138,9 +138,12 @@ static inline bool IsDecimalCharacterUnicode(uint32_t codepoint) {
}

static inline bool IsDigitCharacterUnicode(uint32_t codepoint) {
// Python defines this as Numeric_Type=Digit or Numeric_Type=Decimal.
// utf8proc has no support for this, this is the best we can do:
return HasAnyUnicodeGeneralCategory(codepoint, UTF8PROC_CATEGORY_ND);
// Approximates Python's str.isnumeric():
// returns true for Nd and No (e.g., '٣', '³'), but excludes Nl like Roman numerals
// ('Ⅷ') due to utf8proc limits.
// '¾' (vulgar fraction) is treated as a digit by utf8proc 'No'
return HasAnyUnicodeGeneralCategory(codepoint, UTF8PROC_CATEGORY_ND,
UTF8PROC_CATEGORY_NO);
}

static inline bool IsNumericCharacterUnicode(uint32_t codepoint) {
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