Display hyphenation options for a specific word

Question

When TeX produces Overfull box, is puts something like this in the log:

Overfull \hbox (15.47195pt too wide) in paragraph at lines 7--9
[]\OT1/cmr/m/n/10 I re-ally re-ally want to get dis-played the op-tions for 
hy-phen-ation xxxxxxxxxxxxxx |

I would like a macro \showhyphens that would for an entry like \showhyphens{hyphenation} display its hyphenation options, i.e. hy-phen-ation. This should be displayed either in the document (preferred) or in the log.

(Background: I need this for sumbitting a paper that contains many multi-part words and similar stuff like $(2,3)$-representation etc. I know that there are ways to modify - with \discretionary to make the word breakable, but it makes the code extremly unreadable and I'm not allowed to make this a macro definition.)

Answer 1

Bing! Your wish has been granted.

Seriously: \showhyphens already exists under that exact same name.

Answer 2

Ok, here is the answer for printing the hyphens:

\documentclass[12pt,a4paper]{article}
\def\rehbox{{\unskip\unpenalty\setbox0\lastbox\ifhbox0 \rehbox
    \hbox{\unhbox0} \else \leavevmode \fi}}
\newcommand\printhyphens[1]{%
  \setbox0\vbox{{%
      \pretolerance-1\hsize=0pt\hfuzz=\maxdimen
      \noindent\hspace*{0pt}#1\par\rehbox}\par}%
  \unvbox 0
}

\begin{document}
\printhyphens{If you cannot reconsider this proposal, you are
  incompatible, my dearest friend.}
\end{document}

As the first version is limited by its usage of the save stack, here is a version that isn't. However, as stated in the comments, it is O(n^3), so it will become inefficient for large arguments rather fast, and the whole point of not using the save stack is to be able to use large arguments. So it would really make more sense to first split the input into words or lines and process them one by one, using a call of the first version of \printhyphens.

\documentclass[12pt,a4paper]{article}
\def\rehbox{\unskip\unpenalty\setbox2\lastbox\ifhbox2
  \setbox0\hbox{\hbox{\unhbox2} \unhbox0}\expandafter\rehbox\fi}
\newcommand\printhyphens[1]{%
  \setbox0\vbox{{\setbox0\hbox{}%
      \pretolerance-1\hsize=0pt\hfuzz=\maxdimen
      \noindent\hspace*{0pt}#1\par\rehbox\unhbox0}\par}%
  \unvbox 0
}

\begin{document}
\printhyphens{If you cannot reconsider this proposal, you are
  incompatible, my dearest friend.}
\end{document}

Answer 3

With LuaTeX you have two options: \usepackage{lua-visual-debug} gives a lot of information whereas \usepackage{showhyphens} marks only all possible hyphenation points.

See http://texdoc.net/texmf-dist/doc/lualatex/showhyphens/showhyphens-doc.pdf

Answer 4

Because I know that OP (yo) understand Czech then I can refer the book "TeXbook naruby" (full text available on the internet here), page 225 below and page 226. The macro \showhyphenpar is presented here. The paragraph after \showhyphenpar is printed with all words shown as hy-phen-ated.

\def\showhyphenpar{\bgroup  
   \def\par{\setparams\endgraf\composelines}
   \setbox0=\vbox\bgroup \noindent\hskip0pt\relax}
\def\setparams{\rightskip=0pt plus1fil
   \linepenalty=1000 \pretolerance=-1 \hyphenpenalty=-10000}
\def\composelines{\setbox2=\hbox{}%
   \loop \setbox0=\lastbox \unskip \unpenalty
   \ifhbox0 % je už \vbox vyprázdněn?
     \global\setbox2=\hbox{\unhbox0\unskip\unhbox2}
   \repeat
   \egroup % vyprázdněný \vbox ukončím
   \exhyphenpenalty=10000 % \box2 vyšoupnu do vnějšího seznamu
   \emergencystretch=4em \leavevmode\unhbox2 \endgraf\egroup}

The principles of this macro is described in the TeXbook naruby.