l3kernel

Implements core programming interfaces and conventions for LaTeX3 development, providing essential foundations for modern LaTeX package creation.

Overview

Serves as the fundamental programming layer for LaTeX3, offering a comprehensive API that modernizes LaTeX development and enables more sophisticated package creation. This essential bundle bridges traditional LaTeX2e with modern LaTeX3 conventions.

Provides consistent programming interfaces and conventions for LaTeX developers
Enables modern package development with improved syntax and functionality
Forms the foundation for future LaTeX kernel development
Allows seamless integration of LaTeX3 programming features within LaTeX2e documents
Essential for package authors developing modern LaTeX tools and extensions

Getting Started

To use l3kernel, include it in your document preamble:

\documentclass{article}
\usepackage{expl3}

This package is primarily intended for package authors. The main functionality is:

% Basic LaTeX3 programming example
\ExplSyntaxOn
% LaTeX3 code here
\ExplSyntaxOff

Examples

Basic LaTeX3 programming with expl3 syntax for defining variables and functions.

\documentclass{article}
\usepackage{expl3}

\ExplSyntaxOn
% Define variables
\int_new:N \l_my_counter_int
\int_set:Nn \l_my_counter_int {5}

% Define a function to square a number
\cs_new:Npn \my_square:n #1
{
  \int_eval:n {#1 * #1}
}

% Define a document-level command that uses our function
\NewDocumentCommand{\Square}{m}
{
  The~square~of~#1~is~\my_square:n{#1}.
}
\ExplSyntaxOff

\begin{document}

LaTeX3 programming example:

We defined a counter with value: $\ExplSyntaxOn \int_use:N \l_my_counter_int \ExplSyntaxOff$

Using our square function: \Square{4}

Squaring our counter: \ExplSyntaxOn The~square~of~\int_use:N \l_my_counter_int~is~\my_square:n{\l_my_counter_int}. \ExplSyntaxOff

\end{document}