LATEX News
Issue 27, April 2017 (LATEX release 2017-04-15)

Contents

Disabling hyphenation

ISO 8601 Date format

1

Further TU encoding improvements

1

Disabling hyphenation

1

Discretionary hyphenation

1

Default document language

1Line spacing in parboxes

1

ISO 8601 Date format
Since before the first releases of LATEX 2ε , LATEX has
used a date format in the form yyyy/mm/dd. This has
many advantages over more conventional formats, as it
is easy to sort and avoids the unfortunate ambiguity
between different communities as to whether 01/02/2017
is the 1st of February or 2nd of January.
However there is another date format, formalised by
the International Standard ISO 8601. The basic format
defined by this standard is functionally equivalent to
the LATEX format, but using - rather than /. This dateformat is now supported in many Operating Systems
and applications (for example the date --iso-8601
command in Linux and similar systems).
From this release, LATEX will accept ISO format datestrings in the date argument of \ProvidesPackage,\usepackage, etc. Currently we recommend that you donot use this format in any packages that need to workwith older LATEX releases; the latexrelease package may
be used with older releases to add this functionality.
This change is handled in a special way by latexrelease:
The package always adds support for ISO dates whateverformat date is requested; this is required so that thenecessary date comparisons may be made.
The new functionality can be seen in the startup
banner which advertises LaTeX2e <2017-04-15>.

Further TU encoding improvements
The 2017/01/01 release saw the introduction of the newTU encoding for specifying Unicode fonts with LuaTEX
and XETEX. There were a number of small corrections
and additions in the patch releases updating 2017/01/01,
and a further addition in this release, notably extended
support for the dot-under accent, \d.

The existing LATEX code for \verb and verbatim hadsome issues when used with fonts that were not loadedwith hyphenation disabled via setting \hyphenchar to−1. In this release these verbatim environments use
a \language setting, \l@nohyphenation, that has nohyphenation patterns associated.
The format ensures that a language has been allocatedwith this name. For most users this will in fact be nochange as the standard babel language has for a longtime allocated a language with this name.
In order that page breaks in verbatim do not influence
the language used in the page head and foot, the format
now normalises the language used in the output routine
to a default language as described below.

Discretionary hyphenation
The LATEX definition of \- has been adjusted so that
it will insert the current font’s \hyphenchar, as would
the TEX primitive. A comment in source2e has given
this new definition since the first releases of LATEX 2ε ,and in this release we finally acted upon this comment.
Previously \- always inserted a - at a break point even
if a different character would be used for automatic
hyphenation with the current font.

Default document language
A new integer parameter \document@default@language
is introduced; this is initialised to −1 but is set at\begin{document} to the language in force at thattime if it has not been set by preamble code. This isvery similar to the handling of the default color, and isused in a similar way to normalise the settings for page
head and foot as described above. Users should notnormally need to set this explicitly but it is expectedthat language packages such as babel may set this if thedefault behaviour is not suitable.

Line spacing in parboxes
Inside a \parbox LATEX normalises the baseline spacing.
However it has not previously reset \lineskiplimit.
This meant that lines of a paragraph that have ascenders
or descenders could be set with closer line spacing thanlines without. This can easily happen if you use a\parbox in an AMS alignment, as they use a relatively
large value of \lineskiplimit. As usual, the latexreleasepackage may be used to force the older behavior.

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