Why is caron treated differently than breve

Question

I'm using biblatex and wanted to add the author Kruzhkov into my Bibliography. As far as I see he is written Kru\u{z}kov

Writing him that way leads to an error as here: inputenc Error: Unicode char \u8: not set up for use with LaTeX

If I write Kru\v{z}kov instead everything works fine. I'm using the inputenc package with [utf8] option. Any ideas?

Answer 1

MWE and test file that shows the problem, if compiled without LuaTeX/XeTeX:

\documentclass{article}

\usepackage{ifluatex,ifxetex}
\ifluatex
  \usepackage{fontspec}
\else
  \ifxetex
    \usepackage{fontspec}
  \else
    \usepackage[utf8]{inputenc}
  \fi
\fi

\usepackage[
  backend=biber,
]{biblatex}

\begin{filecontents}{\jobname.bib}
@book{foobar,
  author         = {Kru\u{z}kov and Kru\v{z}kov},
  title          = {About foobar},
  year           = {1970},
}
\end{filecontents}

\addbibresource{\jobname.bib}

\begin{document}
\cite{foobar}
\printbibliography
\end{document}

The program biber normalizes the data input to NFD UTF-8, where all accented characters are decomposed. From its documentation:

3.2 Unicode

Biber uses NFD UTF-8 internally. All data is converted to NFD UTF-8 when read. If UTF-8 output is requested (to .bbl for example), the UTF-8 will always be > NFC.

In the final file \jobname.bib, the decompositions are replaced by equivalent precomposed characters, if these exist.

 LaTeX → internal biber (NFD UTF-8) → output of biber (NFC UTF-8)

 \v{z} → U+007A (z) U+030C (combining caron) → U+017E (latin small letter z with caron)

 \u{z} → U+007A (z) U+0306 (combining breve) → U+007A U+0306

Thus \u{z} remains decomposed and this is a serious problem, because TeX cannot handle combining accents easyly, if they are following the symbol. At this time the accent is seen, the symbol is usually already set and the accent cannot modify the base symbol any more. Even worse, it does not even know the base symbol.

Package ucs can handle combining accents to some degree by looking ahead for combining accents. But this package is not compatible with package biblatex. Also it could get \u{z} working, probably because a precomposed character does not exist for it.

LaTeX's utf8.def for package inputenc cannot handle them.

The following options remain:

• Using \v{z} instead of \u{z}, probably the correct spelling anyway according to the comments.

• The example runs with LuaTeX and XeTeX that can handle the Unicode combining accents.

• Option safeinputenc for package biblatex, see pst's answer.

• Using bibtex instead of biber as backend.

Answer 2

The error is in having the breve in the first place. No language uses z̆ and this is witnessed by the fact that Unicode doesn't have a slot for it. See also Breve (Wikipedia). The glyph z̆ can only be obtained with

U+007A (LATIN SMALL LETTER Z) U+0306 (COMBINING BREVE)

and not as a precomposed character.

If the “American” transliteration of this author's name is Kruzhkov, then the correct diacritic to use is the caron: Kružkov. The error can descend bad interpretation either by a typist or by OCR software. All slavic languages written with the Latin alphabet or transliteration thereof use the caron.

In any case, the only solution is to fix the source to have \v{z}.

---

I believe that the author you're citing is (in American transliteration) Stanislav Nikolaevich Kruzhkov; his name is written in Russian as Станислав Николаевич Кружков (see this entry in mathru.net and the corresponding one in English). The “scientific” transliteration, better called ISO 9, of the name is

Stanislav Nikolaevič Kružkov

and it's not possible to have a breve instead of the caron. See the relevant Wikipedia page.

Answer 3

The problem

Here is the needed MWE:

\begin{filecontents}{\jobname.bib}
@book{withbreve,
  author = {Kru\u{z}kov},
  title = {With Breve},
  year = 2014}
@book{withcaron,
  author = {Kru\v{z}kov},
  title = {With Caron},
  year = 2014}
\end{filecontents}
\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{biblatex}
\addbibresource{\jobname.bib}

\begin{document}
\nocite{*}
\printbibliography
\end{document}

This yields ! Package inputenc Error: Unicode char \u8:̆ not set up for use with LaTeX. The reason is that biber converts everything to Unicode, and sends the converted version back to LaTeX (in the bbl file). The difference between Caron and Breve here is that there is a precomposed Unicode character LATIN SMALL LETTER Z WITH CARON, and that can be handled by LaTeX. For the breve case instead a decomposed form is sent back, and LaTeX can't handle that.

The Fix

A fix to this example is to use \usepackage[safeinputenc]{biblatex}.

Biber needs to do conversions for lots of things, like sorting and for identifying several occurences of the same name. I think it would be better if this was an internal form used only by Biber and not something it sent back. I've reported this as an issue for biber. Even though plk disagreed he has added some more related options in the development version. (See that issue for details.)