Mfcttrf

I want to sort strings (text) in a software project of mine. I'm planning to do this in the lexically best way.

My set of possible characters consist of the full alphabet (a-z and A-Z) and of the typical Latin 1 Umlauts, like "ÄÖÜäöüß" and also characters from other Latin 1 languages like: "àáâã"...

How would one sort those characters so that also humans could look them up fast?

For instance one would seek for Ä after A (I guess). And for é after e.

In which order would "àáâãä" be sorted in between a and b? Is there some kind of ISO standard defining such things? How would those characters be arranged?

Sadly it's technically impossible to order the data by expanding characters like Ä to Ae.

If it's not names you are dealing with, it would be best to ignore all diacritics when sorting (and count ß as ss).

The only reason to deviate from this simple system lies in the unfortunate fact that German names show unpredictable variation between ä, ö, ü and ae, oe, ue. This has lead to phone books and library catalogues sorting e.g. Räder as Raeder, Örtel as Oertel, Hüber as Hueber.

Wikipedia has a good write-up.

Short answer: Take a look at MySQL and different character-collations. Choose one and follow its rules.

Long answer:

There are 3 different solutions for your problem (actually there are 4, but believe me, you don't want to realize the 4th ;) )

1) Rewrite every Umlaut to its base (dictionary rules - DIN 5007-1 var. 1)

Every Umlaut and Diacritic results in the same char.
e.g.

àáâãä = a

ß = ss

and so on.

Sort them.

2) Rewrite every Umlaut by adding an e, diacritics are removed (phone book rules - DIN 5007-1 var. 2)

ä = ae

àáâã = a

ü = ue

ß = ss

Sort them.

3) Umlaute are new chars added to the alphabet (Swedish/Finnish collation rules)

Every Umlaut and chars with diacritics are treated like chars, which are added after the z of the alphabet. Look up different charsets for the sequence of chars with diacretics.

So sort like

abc [...] xyzäàáâãéè ...

I can answer you only regarding the German characters. "Ä" is considered equivalent to "Ae", "Ö" to "Oe", "Ü" to "Ue" and "ß" to "ss". This is how those characters are sorted in a phonebook.