Adequate hyphenation of words already containing a hyphen

Question

Contrary to English, in German there are quite a few words containing a hyphen, e.g. "Arbeiter-Unfallversicherung" (workers' accident insurance). By default, (La)TeX will only break such words after the present hyphen and discard all other breakpoints. This behaviour will often result in overfull hboxes for German texts.

There are at least three ways to achieve proper hyphenation, two of which use shorthands of the babel package and none of which I consider really satisfactory:

1. The "= shorthand: Arbeiter"=Unfallversicherung. This allows every (otherwise legal) breakpoint and therefore may produce correct but unfavourable hyphenation (e.g. Arbeiter-Un-fallversicherung). This seems to be a method of last resort, suited for documents to be created with (almost) no manual intervention.

2. The \- command: Ar\-beiter-Unfall\-ver\-si\-che\-rung. By manually setting allowed breakpoints, one can avoid unfavourable ones shortly before or after a present hyphen (I use a minimum of four characters as a rule of thumb). As a downside, one has to look up the correct breakpoints of the respective words. Also, the body of a LaTeX document may become quite cluttered.

3. The "- shorthand: Ar"-beiter-Unfall"-versicherung. This method (the one I'm currently using) also avoids unfavourable breakpoints and allows for a tidier document body. But one still has to look up the correct breakpoints.

To cut a long story short: Is there a way to automatically allow hyphenation of words already containing a hyphen, discarding breakpoints less than, say, four characters before or after the present hyphen?

Answer 1

No. You could possibly use an external parsing script to apply one of those options to a text, but writing that will be a lot of work still, do manually adding commands is probably less work in practice.

Future update: LuaTeX has rudimentary support for some special hyphenation cases, and in a future version (spring 2011, most likelu) there will be core support for weighted hyphenation and multiple hyphenation passes.

Answer 2

You can set \lefthyphenmin=4 to ensure at least 4 characters after the explicit "= hyphen before any hyphens inserted by tex. (It really sets that there should be 4 characters after the beginning of any word, not only compound words with a "=.)

It's possible to make the change to \lefthyphenmin locally, but it is awkward. Tex only looks at the value of \lefthyphenmin at the beginning of paragraphs and at language changes, so you have to write something like: {\lefthyphenmin4\setlanguage\language ...}\setlanguage\language

Answer 3

This seems to be what the hyphenat package is for. From the manual:

TeX does not want to hyphenate a word that appears in the source already hyphenated, such as electromagnetic-endioscopy.
The \hyp command is like the other \...hyp commands, only it typesets a hyphen and allows full automatic hyphenation of the other words forming the compound word. It is used like electromagnetic\hyp{}endioscopy.

I'm not sure about your last criterion, though it seems that if TeX applies its normal hyphenating rules then this would be unlikely to happen anyway since (I think) that what happens is that the word after the \hyp{} is treated (as far as hyphenation is concerned) as a new word and I guess that not many words get hyphenated in the first (or last) few characters.