LaTeX3 High-Level Concepts

Release 2023-02-02

Overview

The l3packages collection contains implementations for aspects of the LaTeX3 kernel, dealing with higher-level ideas such as the Designer Interface. The packages here are considered broadly stable (The LaTeX Project does not expect the interfaces to alter radically). These packages are build on LaTeX2ε conventions at the interface level, and so may not migrate in the current form to a stand-alone LaTeX3 format.

All of the material in the collection requires the LaTeX3 base layer package l3kernel. The two packages must be installed in matching versions: if you update l3packages, make sure that l3kernel is updated at the same time.

Currently included in the CTAN release of l3packages are the following bundles:

• l3keys2e
• xfp (from 2022-06-01 part of the LaTeX format)
• xfrac
• xparse
• xtemplate

l3keys2e

The l3keys2e package allows keys defined using l3keys to be used as package and class options with LaTeX2ε. This is tied to the method the existing kernel uses for processing options, and so it is likely that a stand-alone LaTeX3 kernel will use a very different approach.

xfp

The xfp package provides a document-level interface for the LaTeX3 FPU. As such, it is a wrapper around the core \fp_eval:n function but does not require code syntax. It provides the expandable command \fpeval, which can be used inside for example \edef or contexts where TeX requires a number. From 2022-06-01 release if LaTeX this will be included in the format so that the package doesn't need loading any longer.

xfrac

The xfrac package uses the interface defined by xtemplate to provide flexible split-level fractions via the \sfrac macro. This is both a demonstration of the power of the template concept and also a useful addition to the available functionality in LaTeX2ε.

xparse (deprecated)

The xparse package provides a high-level interface for declaring document commands, e.g., a uniform way to define commands taking optional arguments, optional stars (and others), mandatory arguments and more.

The development of xparse moved to the LaTeX2ε repository as ltcmd, which is preloaded in the LaTeX format, and the code for xparse in this repository contains only the deprecated argument types G, l, and u.

xtemplate

The xtemplate package provides an interface for defining generic functions using a key=val syntax. This is designed to be "self-documenting", with the key definitions providing information on how they are to be used.

Discussion

Discussion concerning the approach, suggestions for improvements, changes, additions, etc. should be addressed to the list LaTeX-L.

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Issues

The issue tracker for LaTeX3 is currently located on GitHub.

Please report specific issues with LaTeX3 code there; more general discussion should be directed to the LaTeX-L list.

The LaTeX Project

Development of LaTeX3 is carried out by The LaTeX Project.

The development team can be contacted by e-mail: <latex-team@latex-project.org>; for general LaTeX3 discussion the LaTeX-L list should be used.

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