A popular but wrong way to convert a string to uppercase or lowercase

Re:A popular but wrong way to convert a string to uppercase ... by tialaramex on Tuesday October 08, 2024 @06:00PM (#41782226)

Rust will cheerfully:

    assert_eq!("ὀδυσσεύς", "ὈΔΥΣΣΕΎΣ".to_lowercase());

[Notice that this is in fact entirely impossible with the naive strategy since Greek cares about position of symbols]

Some of the latter examples aren't cases where a programming language or library should just "do the right thing" but cases of ambiguity where you need locale information to decide what's appropriate, which isn't "just as wrong as the C++ version" it's a whole other problem. It isn't wrong to capitalise A-acute as a capital A-acute, it's just not always appropriate depending on the locale.

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Re:A popular but wrong way to convert a string to uppercase ... by account42 on Wednesday October 09, 2024 @09:27AM (#41787748)

Is this

    assert_eq!("\u1F41δυσσεύς", "ὈΔΥΣΣΕΎΣ".to_lowercase());

    assert_eq!("\u03BF\u0314δυσσεύς", "ὈΔΥΣΣΕΎΣ".to_lowercase());

For display it doesn't matter but most other applications really want some kind of normalizatin which does much much more so having a convenient to_lowercase() doesn't buy you as much as you think and can be actively misleading.

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