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+\iffalse meta-comment
+
+File: l3syntax-changes.tex
+
+Copyright (C) 2011,2012,2017-2024 The LaTeX Project
+
+It may be distributed and/or modified under the conditions of the
+LaTeX Project Public License (LPPL), either version 1.3c of this
+license or (at your option) any later version. The latest version
+of this license is in the file
+
+ https://www.latex-project.org/lppl.txt
+
+This file is part of the "l3kernel bundle" (The Work in LPPL)
+and all files in that bundle must be distributed together.
+
+The released version of this bundle is available from CTAN.
+
+\fi
+
+\documentclass{l3doc}
+
+
+\title{%
+ Syntax changes in \LaTeX3 functions%
+}
+\author{%
+ The \LaTeX{} Project\thanks
+ {%
+ E-mail:
+ \href{mailto:latex-team@latex-project.org}%
+ {latex-team@latex-project.org}%
+ }%
+}
+\date{Released 2024-04-11}
+
+\newcommand{\TF}{\textit{(TF)}}
+
+\begin{document}
+
+\maketitle
+
+This file describes functions that were expected to be completely
+stable, but whose syntax has changed in ways that may potentially
+require code relying on them to be changed. This file does not include
+bug-fixes, nor backward-compatible extensions of the syntax,
+nor functions that were completely
+deprecated: the latter are listed in \texttt{l3obsolete.txt}. Only
+changes after August 2011 are listed, with an approximate date.
+
+\section{August 2011}
+
+\begin{itemize}
+ \item \cs{tl_if_single:n\TF} recognized any non-zero number of
+ explicit spaces as \meta{true}, and did not ignore trailing spaces.
+ Now it is \meta{true} for
+ \[
+ \meta{optional spaces}
+ \meta{normal token or brace group}
+ \meta{optional spaces}.
+ \]
+ \item \cs{tl_reverse:n} stripped outer braces and lost unprotected spaces.
+ Now it keeps spaces, leaves unbraced single tokens unbraced, and
+ braced groups braced.
+ \item \cs{tl_trim_spaces:n} only removed one leading and trailing space.
+ Now removes recursively. Also, on the left it used to strip implicit
+ and explicit spaces with any character code. Now it strips only explicit
+ space characters $(32,10)$.
+\end{itemize}
+
+\section{September 2011}
+
+\begin{itemize}
+\item clist functions which receive an \texttt{n}-type comma list argument
+ now trim spaces from each item in the argument.
+\end{itemize}
+
+\section{May 2012}
+
+\begin{itemize}
+ \item The \pkg{l3fp} code has been completely rewritten with a new
+ expandable interface.
+ \item Getting/popping from a comma list or sequence or property list
+ that is empty (or missing the given key) now gives the quark
+ \cs{q_no_value}.
+\end{itemize}
+
+\section{June 2012}
+
+\begin{itemize}
+ \item Access to list functions now indexes from~$1$, not from~$0$.
+ This applies to multiple choices in the \pkg{l3keys} module and
+ the \cs{clist_item:Nn}, \cs{seq_item:Nn} and \cs{tl_item:Nn}
+ functions.
+ \item \cs{tl_trim_spaces:n} now requires a variable number of
+ expansions to fully expand, rather than exactly two. Of course,
+ \texttt{x}-type or \texttt{e}-type expansion still correctly evaluates this function.
+\end{itemize}
+
+\section{July 2012}
+
+\begin{itemize}
+ \item The \cs{tl_if_head_eq_meaning:nN}, \cs{tl_if_head_eq_catcode:nN}
+ and \cs{tl_if_head_eq_charcode:nN} conditionals now never match when
+ their first argument is empty.
+\end{itemize}
+
+\section{August 2012}
+
+\begin{itemize}
+ \item \cs{lua_now:x} is now a standard \texttt{x}-type expansion of
+ \cs{lua_now:n}, which does no expansion. Engine-level expansion is moved
+ to \cs{lua_now:e}, reflecting the fact that this is non-standard in the
+ same way as for example \cs{str_if_eq_x:nn(TF)}.
+\end{itemize}
+
+\section{December 2013}
+
+\begin{itemize}
+ \item In \pkg{l3fp} expressions, the badly named functions |round0|,
+ |round-|, |round+| are now named |trunc|, |floor|, |ceil|.
+\end{itemize}
+
+\section{May 2014}
+
+\begin{itemize}
+ \item Now \cs{int_step_function:nnnN} evaluates its first three
+ arguments (start, step, stop) up front, rather than evaluating them
+ at each step in the loop. The same holds for the related mappings
+ \cs{int_step_inline:nnnn}, \cs{int_step_variable:nnnNn}, and their
+ analogues for \texttt{dim} and \texttt{fp} datatypes.
+\end{itemize}
+
+\section{July 2014}
+
+\begin{itemize}
+ \item In \pkg{l3fp} expressions, juxtaposition is interpreted as
+ multiplication. Now the precedence of juxtaposition is set to be
+ the same as if there was an explicit multiplication
+ sign~\texttt{*}. Previously, juxtaposition would bound more tightly
+ than any other operation.
+\end{itemize}
+
+\section{August 2015}
+
+\begin{itemize}
+ \item The \cs{hbox:n} and related \pkg{l3box} commands now take an
+ \texttt{n}-type argument and provide it braced to the underlying
+ \TeX{} primitive. The functions \cs{hbox:w} and \cs{hbox_end:} in
+ contrast do not read the contents of the box as a macro argument.
+\end{itemize}
+
+\section{2016}
+
+No change.
+
+\section{July 2017}
+
+\begin{itemize}
+ \item Boolean expressions are now evaluated eagerly, namely both
+ operands of logical \texttt{and} (|&&|) and \texttt{or} (\verb"||")
+ are evaluated even when the result of the logical operation is fixed
+ after determining the first operand. For lazy evaluation,
+ \cs{bool_lazy_and_p:nn} and related functions are provided.
+\end{itemize}
+
+\section{November 2017}
+
+\begin{itemize}
+ \item Spaces are now preserved inside keys in \pkg{l3keys}, and
+ trimmed at both ends.
+ \item \cs{cs_generate_variant:Nn} is now stricter: it only allows to
+ change \texttt{N}-type arguments to \texttt{c}, and \texttt{n} to
+ \texttt{o}, \texttt{V}, \texttt{v}, \texttt{f}, \texttt{x}. On the
+ one hand the latter argument types typically give rise to more than
+ one token, not suitable for use by an \texttt{N}-type base function.
+ On the other hand, \texttt{c} variants of \texttt{n} arguments
+ should often be \texttt{v} variants (when the argument is eventually
+ evaluated) or mistakes where the programmer thought the base
+ function was \texttt{N}-type.
+\end{itemize}
+
+\section{February 2020}
+
+\begin{itemize}
+ \item \cs{keyval_parse:NNn} now works by expansion, returning
+ the parsed list inside \cs{exp_not:n}.
+\end{itemize}
+
+\end{document}