When you typeset long pathnames, electronic mail addresses, or other
such "computer" names, you would like TeX to break lines at
punctuation characters within the name, rather than trying to find
hyphenation points within the words. For example, it would be better to
break the email address letters@alpha.gnu.ai.mit.edu at the
`@' or a `.', rather than at the hyphenation points in
`letters' and `alpha'.
If you use the \path macro to typeset the names, TeX will find
these good breakpoints. The argument to \path is delimited by
any other other than `\' which does not appear in the name itself.
`|' is often a good choice, as in:
\path|letters@alpha.gnu.ai.mit.edu|
You can control the exact set of characters at which breakpoints will be
allowed by calling \discretionaries. This takes the same sort of
delimited argument; any character in the argument will henceforth be a valid
breakpoint within \path. The default set is essentially all the
punctuation characters:
\discretionaries |~!@$%^&*()_+`-=#{}[]:";'<>,.?\/|
If for some reason you absolutely must use \ as the delimiter
character for \path, you can set
\specialpathdelimiterstrue. (Other delimiter characters can
still be used.) TeX then processes the \path argument
about four times more slowly.