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%% File: l3expan.dtx
%
% Copyright (C) 1990-2024 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 development version of the bundle can be found at
%
% https://github.com/latex3/latex3
%
% for those people who are interested.
%
%<*driver>
\documentclass[full,kernel]{l3doc}
\begin{document}
\DocInput{\jobname.dtx}
\end{document}
%
% \fi
%
% \title{^^A
% The \pkg{l3expan} module\\ Argument expansion^^A
% }
%
% \author{^^A
% The \LaTeX{} Project\thanks
% {^^A
% E-mail:
% \href{mailto:latex-team@latex-project.org}
% {latex-team@latex-project.org}^^A
% }^^A
% }
%
% \date{Released 2024-03-14}
%
% \maketitle
%
% \begin{documentation}
%
% This module provides generic methods for expanding \TeX{} arguments in a
% systematic manner. The functions in this module all have prefix |exp|.
%
% Not all possible variations are implemented for every base
% function. Instead only those that are used within the \LaTeX3 kernel
% or otherwise seem to be of general interest are implemented.
% Consult the module description to find out which functions are
% actually defined. The next section explains how to define missing
% variants.
%
% \section{Defining new variants}
% \label{sec:l3expan:defining-variants}
%
% The definition of variant forms for base functions may be necessary
% when writing new functions or when applying a kernel function in a
% situation that we haven't thought of before.
%
% Internally preprocessing of arguments is done with functions of the form
% \cs[no-index]{exp_\ldots{}}. They all look alike, an example would be
% \cs{exp_args:NNo}. This function has three arguments, the first and the
% second are a single tokens, while the third argument should be given
% in braces. Applying \cs{exp_args:NNo} expands the content of third
% argument once before any expansion of the first and second arguments.
% If \cs{seq_gpush:No} was not defined it could be coded in the following way:
% \begin{verbatim}
% \exp_args:NNo \seq_gpush:Nn
% \g_file_name_stack
% { \l_tmpa_tl }
% \end{verbatim}
% In other words, the first argument to \cs{exp_args:NNo} is the base
% function and the other arguments are preprocessed and then passed to
% this base function. In the example the first argument to the base
% function should be a single token which is left unchanged while the
% second argument is expanded once. From this example we can also see
% how the variants are defined. They just expand into the appropriate
% |\exp_| function followed by the desired base function, \emph{e.g.}
% \begin{quote}
% |\cs_generate_variant:Nn \seq_gpush:Nn { No } |
% \end{quote}
% results in the definition of |\seq_gpush:No|
% \begin{quote}
% |\cs_new:Npn \seq_gpush:No { \exp_args:NNo \seq_gpush:Nn }|
% \end{quote}
% Providing variants in this way in style files is safe as the
% \cs{cs_generate_variant:Nn} function will only create new definitions if
% there is not already one available. Therefore adding
% such definition to later releases of the kernel will not make such
% style files obsolete.
%
% The steps above may be automated by using the function
% \cs{cs_generate_variant:Nn}, described next.
%
% \section{Methods for defining variants}
% \label{sec:l3expan:variants-method}
%
% We recall the set of available argument specifiers.
% \begin{itemize}
% \item |N|~is used for single-token arguments while |c|~constructs a
% control sequence from its name and passes it to a parent function as
% an |N|-type argument.
% \item Many argument types extract or expand some tokens and provide it
% as an |n|-type argument, namely a braced multiple-token argument:
% |V|~extracts the value of a variable, |v|~extracts the value from
% the name of a variable, |n|~uses the argument as it is, |o|~expands
% once, |f|~expands fully the front of the token list, |e| and
% |x|~expand fully all tokens (differences are explained later).
% \item A few odd argument types remain: |T|~and |F|~for conditional
% processing, otherwise identical to |n|-type arguments,
% |p|~for the parameter text
% in definitions, |w|~for arguments with a specific syntax, and |D|~to
% denote primitives that should not be used directly.
% \end{itemize}
%
% \begin{function}[updated = 2017-11-28]
% {\cs_generate_variant:Nn, \cs_generate_variant:cn}
% \begin{syntax}
% \cs{cs_generate_variant:Nn} \meta{parent control sequence} \Arg{variant argument specifiers}
% \end{syntax}
% This function is used to define argument-specifier variants of the
% \meta{parent control sequence} for \LaTeX3 code-level macros. The
% \meta{parent control sequence} is first separated into the
% \meta{base name} and \meta{original argument specifier}. The
% comma-separated list of \meta{variant argument specifiers} is
% then used to define variants of the
% \meta{original argument specifier} if these are not already
% defined; entries which correspond to existing functions are silently
% ingored. For each \meta{variant} given, a function is created
% that expands its arguments as detailed and passes them
% to the \meta{parent control sequence}. So for example
% \begin{verbatim}
% \cs_set:Npn \foo:Nn #1#2 { code here }
% \cs_generate_variant:Nn \foo:Nn { c }
% \end{verbatim}
% creates a new function |\foo:cn| which expands its first
% argument into a control sequence name and passes the result to
% |\foo:Nn|. Similarly
% \begin{verbatim}
% \cs_generate_variant:Nn \foo:Nn { NV , cV }
% \end{verbatim}
% generates the functions |\foo:NV| and |\foo:cV| in the same
% way. The \cs{cs_generate_variant:Nn} function should only be applied if
% the \meta{parent control sequence} is already defined. (This is only
% enforced if debugging support \texttt{check-declarations} is enabled.)
% If the \meta{parent
% control sequence} is protected or if the \meta{variant} involves any
% |x|~argument, then the \meta{variant control sequence} is also
% protected. The \meta{variant} is created globally, as is any
% \cs[no-index]{exp_args:N\meta{variant}} function needed to carry out the
% expansion. There is no need to re-apply \cs{cs_generate_variant:Nn} after
% changing the definition of the parent function: the variant will always
% use the current definition of the parent. Providing variants repeatedly is
% safe as \cs{cs_generate_variant:Nn} will only create new definitions if
% there is not already one available.
%
% Only |n|~and |N| arguments can be changed to other types. The only
% allowed changes are
% \begin{itemize}
% \item |c|~variant of an |N|~parent;
% \item |o|, |V|, |v|, |f|, |e|, or~|x| variant of an |n|~parent;
% \item |N|, |n|, |T|, |F|, or |p| argument unchanged.
% \end{itemize}
% This means the \meta{parent} of a \meta{variant} form is always
% unambiguous, even in cases where both an |n|-type parent and an
% |N|-type parent exist, such as for \cs{tl_count:n} and
% \cs{tl_count:N}.
%
% When creating variants for conditional functions,
% \cs{prg_generate_conditional_variant:Nnn} provides a convenient way
% of handling the related function set.
%
% For backward compatibility it is currently possible to make |n|,
% |o|, |V|, |v|, |f|, |e|, or |x|-type variants of an |N|-type argument or
% |N| or |c|-type variants of an |n|-type argument. Both are
% deprecated. The first because passing more than one token to an
% |N|-type argument will typically break the parent function's code.
% The second because programmers who use that most often want to
% access the value of a variable given its name, hence should use a
% |V|-type or |v|-type variant instead of |c|-type. In those cases,
% using the lower-level \cs{exp_args:No} or \cs{exp_args:Nc}
% functions explicitly is preferred to defining confusing variants.
% \end{function}
%
% \begin{function}[added = 2018-04-04, updated = 2019-02-08]
% {\exp_args_generate:n}
% \begin{syntax}
% \cs{exp_args_generate:n} \Arg{variant argument specifiers}
% \end{syntax}
% Defines \cs[no-index]{exp_args:N\meta{variant}} functions for each
% \meta{variant} given in the comma list \Arg{variant argument
% specifiers}. Each \meta{variant} should consist of the letters |N|,
% |c|, |n|, |V|, |v|, |o|, |f|, |e|, |x|, |p| and the resulting function is
% protected if the letter |x| appears in the \meta{variant}. This is
% only useful for cases where \cs{cs_generate_variant:Nn} is not
% applicable.
% \end{function}
%
% \section{Introducing the variants}
%
% The |V| type returns the value of a register, which can be one of
% |tl|, |clist|, |int|, |skip|, |dim|, |muskip|, or built-in \TeX{}
% registers. The |v| type is the same except it first creates a
% control sequence out of its argument before returning the
% value.
%
% In general, the programmer should not need to be concerned with
% expansion control. When simply using the content of a variable,
% functions with a |V| specifier should be used. For those referred to by
% (cs)name, the |v| specifier is available for the same purpose. Only when
% specific expansion steps are needed, such as when using delimited
% arguments, should the lower-level functions with |o| specifiers be employed.
%
% The |e| type expands all tokens fully, starting from the first. More
% precisely the expansion is identical to that of \TeX{}'s \tn{message}
% (in particular |#| needs not be doubled). It relies on the
% primitive \tn{expanded} hence is fast.
%
% The |x| type expands all tokens fully, starting from the first. In
% contrast to |e|, all macro parameter characters |#| must be doubled,
% and omitting this leads to low-level errors. In addition this type of
% expansion is not expandable, namely functions that have |x| in their
% signature do not themselves expand when appearing inside |e| or |x|
% expansion.
%
% The |f| type is so special that it deserves an example. It is
% typically used in contexts where only expandable commands are allowed.
% Then |x|-expansion cannot be used, and |f|-expansion provides an
% alternative that expands the front of the token list
% as much as can be done in such contexts. For
% instance, say that we want to evaluate the integer expression $3 + 4$
% and pass the result $7$ as an argument to an expandable function
% |\example:n|. For this, one should define a variant using
% \cs{cs_generate_variant:Nn} |\example:n| |{| |f| |}|, then do
% \begin{quote}
% |\example:f { \int_eval:n { 3 + 4 } }|
% \end{quote}
% Note that |x|-expansion would also expand \cs{int_eval:n} fully to its
% result~$7$, but the variant |\example:x| cannot be expandable. Note
% also that |o|-expansion would not expand \cs{int_eval:n} fully to its
% result since that function requires several expansions. Besides the
% fact that |x|-expansion is protected rather than expandable, another
% difference between |f|-expansion and |x|-expansion is that
% |f|-expansion expands tokens from the beginning and stops as soon as a
% non-expandable token is encountered, while |x|-expansion continues
% expanding further tokens. Thus, for instance
% \begin{quote}
% |\example:f { \int_eval:n { 1 + 2 } , \int_eval:n { 3 + 4 } }|
% \end{quote}
% results in the call
% \begin{quote}
% |\example:n { 3 , \int_eval:n { 3 + 4 } }|
% \end{quote}
% while using |\example:x| or |\example:e| instead results in
% \begin{quote}
% |\example:n { 3 , 7 }|
% \end{quote}
% at the cost of being protected for |x|-type.
% If you use |f| type expansion in conditional processing then
% you should stick to using |TF| type functions only as the expansion
% does not finish any |\if... \fi:| itself!
%
% It is important to note that both \texttt{f}- and \texttt{o}-type
% expansion are concerned with the expansion of tokens from left to
% right in their arguments. In particular, \texttt{o}-type expansion
% applies to the first \emph{token} in the argument it receives: it
% is conceptually similar to
% \begin{verbatim}
% \exp_after:wN \exp_after:wN { }
% \end{verbatim}
% At the same time, \texttt{f}-type expansion stops at the \emph{first}
% non-expandable token. This means for example that both
% \begin{verbatim}
% \tl_set:No \l_tmpa_tl { { \g_tmpb_tl } }
% \end{verbatim}
% and
% \begin{verbatim}
% \tl_set:Nf \l_tmpa_tl { { \g_tmpb_tl } }
% \end{verbatim}
% leave |\g_tmpb_tl| unchanged: |{| is the first token in the
% argument and is non-expandable.
%
% It is usually best to keep the following in mind when using variant
% forms.
% \begin{itemize}
% \item
% Variants with |x|-type arguments (that are fully expanded before
% being passed to the |n|-type base function) are never expandable
% even when the base function is. Such variants cannot work
% correctly in arguments that are themselves subject to expansion.
% Consider using |f| or |e| expansion.
% \item
% In contrast, |e|~expansion (full expansion, almost like~|x| except
% for the treatment of~|#|) does not prevent variants from being
% expandable (if the base function is).
% \item
% Finally |f|~expansion only expands the front of the token list,
% stopping at the first non-expandable token. This may fail to
% fully expand the argument.
% \end{itemize}
%
% When speed is essential (for functions that do very little work and
% whose variants are used numerous times in a document) the following
% considerations apply because the speed of internal functions that
% expand the arguments of a base function depend on what needs doing
% with each argument and where this happens in the list of arguments:
% \begin{itemize}
% \item for fastest processing any |c|-type arguments should come first
% followed by all other modified arguments;
% \item unchanged |N|-type args that appear before modified ones have
% a small performance hit;
% \item unchanged |n|-type args that appear before modified ones have
% a relative larger performance hit.
% \end{itemize}
%
% \section{Manipulating the first argument}
%
% These functions are described in detail: expansion of multiple tokens follows
% the same rules but is described in a shorter fashion.
%
% \begin{function}[EXP]{\exp_args:Nc, \exp_args:cc}
% \begin{syntax}
% \cs{exp_args:Nc} \meta{function} \Arg{tokens}
% \end{syntax}
% This function absorbs two arguments (the \meta{function} name and
% the \meta{tokens}). The \meta{tokens} are expanded until only characters
% remain, and are then turned into a control sequence.
% The result is inserted into the input stream \emph{after} reinsertion
% of the \meta{function}. Thus the \meta{function} may take more than
% one argument: all others are left unchanged.
%
% The |:cc| variant constructs the \meta{function} name in the same
% manner as described for the \meta{tokens}.
% \end{function}
%
% \begin{function}[EXP]{\exp_args:No}
% \begin{syntax}
% \cs{exp_args:No} \meta{function} \Arg{tokens} ...
% \end{syntax}
% This function absorbs two arguments (the \meta{function} name and
% the \meta{tokens}). The \meta{tokens} are expanded once, and the result
% is inserted in braces into the input stream \emph{after} reinsertion
% of the \meta{function}. Thus the \meta{function} may take more than
% one argument: all others are left unchanged.
% \end{function}
%
% \begin{function}[EXP]{\exp_args:NV}
% \begin{syntax}
% \cs{exp_args:NV} \meta{function} \meta{variable}
% \end{syntax}
% This function absorbs two arguments (the names of the \meta{function} and
% the \meta{variable}). The content of the \meta{variable} are recovered
% and placed inside braces into the input stream \emph{after} reinsertion
% of the \meta{function}. Thus the \meta{function} may take more than
% one argument: all others are left unchanged.
% \end{function}
%
% \begin{function}[EXP]{\exp_args:Nv}
% \begin{syntax}
% \cs{exp_args:Nv} \meta{function} \Arg{tokens}
% \end{syntax}
% This function absorbs two arguments (the \meta{function} name and
% the \meta{tokens}). The \meta{tokens} are expanded until only characters
% remain, and are then turned into a control sequence.
% This control sequence should
% be the name of a \meta{variable}. The content of the \meta{variable} are
% recovered and placed inside braces into the input stream \emph{after}
% reinsertion of the \meta{function}. Thus the \meta{function} may take more
% than one argument: all others are left unchanged.
% \end{function}
%
% \begin{function}[EXP, added = 2018-05-15]{\exp_args:Ne}
% \begin{syntax}
% \cs{exp_args:Ne} \meta{function} \Arg{tokens}
% \end{syntax}
% This function absorbs two arguments (the \meta{function} name and
% the \meta{tokens}) and exhaustively expands the \meta{tokens}.
% The result is inserted in braces into the input stream
% \emph{after} reinsertion of the \meta{function}.
% Thus the \meta{function} may take more
% than one argument: all others are left unchanged.
% \end{function}
%
% \begin{function}[EXP]{\exp_args:Nf}
% \begin{syntax}
% \cs{exp_args:Nf} \meta{function} \Arg{tokens}
% \end{syntax}
% This function absorbs two arguments (the \meta{function} name and
% the \meta{tokens}). The \meta{tokens} are fully expanded until the
% first non-expandable token is found (if that is a space it is
% removed), and the result
% is inserted in braces into the input stream \emph{after} reinsertion
% of the \meta{function}. Thus the \meta{function} may take more than
% one argument: all others are left unchanged.
% \end{function}
%
% \begin{function}{\exp_args:Nx}
% \begin{syntax}
% \cs{exp_args:Nx} \meta{function} \Arg{tokens}
% \end{syntax}
% This function absorbs two arguments (the \meta{function} name and
% the \meta{tokens}) and exhaustively expands the \meta{tokens}.
% The result is inserted in braces into the input stream
% \emph{after} reinsertion of the \meta{function}.
% Thus the \meta{function} may take more
% than one argument: all others are left unchanged.
% \end{function}
%
% \section{Manipulating two arguments}
%
% \begin{function}[EXP, updated = 2018-05-15]
% {
% \exp_args:NNc,
% \exp_args:NNo,
% \exp_args:NNV,
% \exp_args:NNv,
% \exp_args:NNe,
% \exp_args:NNf,
% \exp_args:Ncc,
% \exp_args:Nco,
% \exp_args:NcV,
% \exp_args:Ncv,
% \exp_args:Ncf,
% \exp_args:NVV
% }
% \begin{syntax}
% \cs{exp_args:NNc} \meta{token_1} \meta{token_2} \Arg{tokens}
% \end{syntax}
% These optimized functions absorb three arguments and expand the second and
% third as detailed by their argument specifier. The first argument
% of the function is then the next item on the input stream, followed
% by the expansion of the second and third arguments.
% \end{function}
%
% \begin{function}[EXP, updated = 2018-05-15]
% {
% \exp_args:Nnc,
% \exp_args:Nno,
% \exp_args:NnV,
% \exp_args:Nnv,
% \exp_args:Nne,
% \exp_args:Nnf,
% \exp_args:Noc,
% \exp_args:Noo,
% \exp_args:Nof,
% \exp_args:NVo,
% \exp_args:Nfo,
% \exp_args:Nff,
% \exp_args:Nee,
% }
% \begin{syntax}
% \cs{exp_args:Noo} \meta{token} \Arg{tokens_1} \Arg{tokens_2}
% \end{syntax}
% These functions absorb three arguments and expand the second and
% third as detailed by their argument specifier. The first argument
% of the function is then the next item on the input stream, followed
% by the expansion of the second and third arguments.
% \end{function}
%
% \begin{function}
% {
% \exp_args:NNx,
% \exp_args:Ncx,
% \exp_args:Nnx,
% \exp_args:Nox,
% \exp_args:Nxo,
% \exp_args:Nxx
% }
% \begin{syntax}
% \cs{exp_args:NNx} \meta{token_1} \meta{token_2} \Arg{tokens}
% \end{syntax}
% These functions absorb three arguments and expand the second and
% third as detailed by their argument specifier. The first argument
% of the function is then the next item on the input stream, followed
% by the expansion of the second and third arguments. These functions
% are not expandable due to their |x|-type argument.
% \end{function}
%
% \section{Manipulating three arguments}
%
% \begin{function}[EXP]
% {
% \exp_args:NNNo,
% \exp_args:NNNV,
% \exp_args:NNNv,
% \exp_args:NNNe,
% \exp_args:Nccc,
% \exp_args:NcNc,
% \exp_args:NcNo,
% \exp_args:Ncco
% }
% \begin{syntax}
% \cs{exp_args:NNNo} \meta{token_1} \meta{token_2} \meta{token_3} \Arg{tokens}
% \end{syntax}
% These optimized functions absorb four arguments and expand the second, third
% and fourth as detailed by their argument specifier. The first
% argument of the function is then the next item on the input stream,
% followed by the expansion of the second argument, \emph{etc}.
% \end{function}
%
% \begin{function}[EXP]
% {
% \exp_args:NNcf,
% \exp_args:NNno,
% \exp_args:NNnV,
% \exp_args:NNoo,
% \exp_args:NNVV,
% \exp_args:Ncno,
% \exp_args:NcnV,
% \exp_args:Ncoo,
% \exp_args:NcVV,
% \exp_args:Nnnc,
% \exp_args:Nnno,
% \exp_args:Nnnf,
% \exp_args:Nnff,
% \exp_args:Nooo,
% \exp_args:Noof,
% \exp_args:Nffo,
% \exp_args:Neee
% }
% \begin{syntax}
% \cs{exp_args:NNoo} \meta{token_1} \meta{token_2} \Arg{token_3} \Arg{tokens}
% \end{syntax}
% These functions absorb four arguments and expand the second, third
% and fourth as detailed by their argument specifier. The first
% argument of the function is then the next item on the input stream,
% followed by the expansion of the second argument, \emph{etc}.
% \end{function}
%
% \begin{function}[added = 2015-08-12]
% {
% \exp_args:NNNx,
% \exp_args:NNnx,
% \exp_args:NNox,
% \exp_args:Nccx,
% \exp_args:Ncnx,
% \exp_args:Nnnx,
% \exp_args:Nnox,
% \exp_args:Noox,
% }
% \begin{syntax}
% \cs{exp_args:NNnx} \meta{token_1} \meta{token_2} \Arg{tokens_1} \Arg{tokens_2}
% \end{syntax}
% These functions absorb four arguments and expand the second, third
% and fourth as detailed by their argument specifier. The first
% argument of the function is then the next item on the input stream,
% followed by the expansion of the second argument, \emph{etc.}
% \end{function}
%
% \section{Unbraced expansion}
%
% \begin{function}[EXP, updated = 2018-05-15]
% {
% \exp_last_unbraced:No,
% \exp_last_unbraced:NV,
% \exp_last_unbraced:Nv,
% \exp_last_unbraced:Ne,
% \exp_last_unbraced:Nf,
% \exp_last_unbraced:NNo,
% \exp_last_unbraced:NNV,
% \exp_last_unbraced:NNf,
% \exp_last_unbraced:Nco,
% \exp_last_unbraced:NcV,
% \exp_last_unbraced:Nno,
% \exp_last_unbraced:Nnf,
% \exp_last_unbraced:Noo,
% \exp_last_unbraced:Nfo,
% \exp_last_unbraced:NNNo,
% \exp_last_unbraced:NNNV,
% \exp_last_unbraced:NNNf,
% \exp_last_unbraced:NnNo,
% \exp_last_unbraced:NNNNo,
% \exp_last_unbraced:NNNNf,
% }
% \begin{syntax}
% \cs{exp_last_unbraced:Nno} \meta{token} \Arg{tokens_1} \Arg{tokens_2}
% \end{syntax}
% These functions absorb the number of arguments given by their
% specification, carry out the expansion
% indicated and leave the results in the input stream, with the
% last argument not surrounded by the usual braces.
% Of these, the |:Nno|, |:Noo|, |:Nfo| and |:NnNo|
% variants need slower processing.
% \begin{texnote}
% As an optimization, the last argument is unbraced by some
% of those functions before expansion. This can cause problems
% if the argument is empty: for instance,
% \cs{exp_last_unbraced:Nf} |\foo_bar:w| |{ }| \cs{q_stop}
% leads to an infinite loop, as the quark is \texttt{f}-expanded.
% \end{texnote}
% \end{function}
%
% \begin{function}{\exp_last_unbraced:Nx}
% \begin{syntax}
% \cs{exp_last_unbraced:Nx} \meta{function} \Arg{tokens}
% \end{syntax}
% This function fully expands the \meta{tokens} and leaves the result
% in the input stream after reinsertion of the \meta{function}.
% This function is not expandable.
% \end{function}
%
% \begin{function}[EXP]{\exp_last_two_unbraced:Noo}
% \begin{syntax}
% \cs{exp_last_two_unbraced:Noo} \meta{token} \Arg{tokens_1} \Arg{tokens_2}
% \end{syntax}
% This function absorbs three arguments and expands the second and third
% once. The first argument of the function is then the next item on the
% input stream, followed by the expansion of the second and third arguments,
% which are not wrapped in braces.
% This function needs special (slower) processing.
% \end{function}
%
% \begin{function}[EXP]{\exp_after:wN}
% \begin{syntax}
% \cs{exp_after:wN} \meta{token_1} \meta{token_2}
% \end{syntax}
% Carries out a single expansion of \meta{token_2} (which may consume
% arguments) prior to the expansion of \meta{token_1}. If \meta{token_2} has
% no expansion (for example, if it is a character) then it is left
% unchanged. It is important to notice that \meta{token_1} may be
% \emph{any} single token, including group-opening and -closing
% tokens (|{| or |}| assuming normal \TeX{} category codes). Unless
% specifically required this should be avoided: expansion should be carried out using an
% appropriate argument specifier variant or the appropriate
% \cs[no-index]{exp_args:N\meta{variant}} function.
% \begin{texnote}
% This is the \TeX{} primitive \tn{expandafter}.
% \end{texnote}
% \end{function}
%
%
% \section{Preventing expansion}
%
% Despite the fact that the following functions are all about preventing
% expansion, they're designed to be used in an expandable context and hence
% are all marked as being `expandable' since they themselves disappear
% after the expansion has completed.
%
% \begin{function}[EXP]{\exp_not:N}
% \begin{syntax}
% \cs{exp_not:N} \meta{token}
% \end{syntax}
% Prevents expansion of the \meta{token} in a context where it would
% otherwise be expanded, for example an |e|-type or |x|-type argument or
% the first token in an |o|-type or |f|-type argument.
% \begin{texnote}
% This is the \TeX{} primitive \tn{noexpand}. It only prevents
% expansion. At the beginning of an |f|-type argument, a space
% \meta{token} is removed even if it appears as \cs{exp_not:N}
% \cs{c_space_token}. In an |e|-expanding definition
% (\cs{cs_new:Npe}), a macro parameter introduces an argument even
% if it appears as \cs{exp_not:N} |#| |1|. This differs from
% \cs{exp_not:n}.
% \end{texnote}
% \end{function}
%
% \begin{function}[EXP]{\exp_not:c}
% \begin{syntax}
% \cs{exp_not:c} \Arg{tokens}
% \end{syntax}
% Expands the \meta{tokens} until only characters remain, and then
% converts this into a control sequence.
% Further expansion of this control sequence is then inhibited using
% \cs{exp_not:N}.
% \end{function}
%
% \begin{function}[EXP]{\exp_not:n}
% \begin{syntax}
% \cs{exp_not:n} \Arg{tokens}
% \end{syntax}
% Prevents expansion of the \meta{tokens} in an |e|-type or |x|-type argument.
% In all other cases the \meta{tokens} continue to be expanded, for
% example in the input stream or in other types of arguments such as
% \texttt{c}, \texttt{f}, \texttt{v}. The argument of \cs{exp_not:n}
% \emph{must} be surrounded by braces.
% \begin{texnote}
% This is the \eTeX{} primitive \tn{unexpanded}. In an
% |e|-expanding definition (\cs{cs_new:Npe}), \cs{exp_not:n}~|{#1}|
% is equivalent to |##1| rather than to~|#1|, namely it inserts the
% two characters |#| and~|1|, and
% \cs{exp_not:n}~|{#}| is equivalent to |#|, namely it inserts the
% character~|#|.
% \end{texnote}
% \end{function}
%
% \begin{function}[EXP]{\exp_not:o}
% \begin{syntax}
% \cs{exp_not:o} \Arg{tokens}
% \end{syntax}
% Expands the \meta{tokens} once, then prevents any further expansion
% in |e|-type or |x|-type arguments using \cs{exp_not:n}.
% \end{function}
%
% \begin{function}[EXP]{\exp_not:V}
% \begin{syntax}
% \cs{exp_not:V} \meta{variable}
% \end{syntax}
% Recovers the content of the \meta{variable}, then prevents expansion
% of this material in |e|-type or |x|-type arguments using \cs{exp_not:n}.
% \end{function}
%
% \begin{function}[EXP]{\exp_not:v}
% \begin{syntax}
% \cs{exp_not:v} \Arg{tokens}
% \end{syntax}
% Expands the \meta{tokens} until only characters remains, and then
% converts this into a control sequence which should be a \meta{variable}
% name.
% The content of the \meta{variable} is recovered, and further
% expansion in |e|-type or |x|-type arguments is prevented using \cs{exp_not:n}.
% \end{function}
%
% \begin{function}[EXP]{\exp_not:e}
% \begin{syntax}
% \cs{exp_not:e} \Arg{tokens}
% \end{syntax}
% Expands \meta{tokens} exhaustively, then protects the result of the
% expansion (including any tokens which were not expanded) from
% further expansion in |e|-type or |x|-type arguments using \cs{exp_not:n}.
% This is very rarely useful but is provided for consistency.
% \end{function}
%
% \begin{function}[EXP]{\exp_not:f}
% \begin{syntax}
% \cs{exp_not:f} \Arg{tokens}
% \end{syntax}
% Expands \meta{tokens} fully until the first unexpandable token is
% found (if it is a space it is removed). Expansion then stops, and
% the result of the expansion (including any tokens which were not
% expanded) is protected from further expansion in |e|-type or |x|-type arguments
% using \cs{exp_not:n}.
% \end{function}
%
% \begin{function}[updated = 2011-06-03, EXP]{\exp_stop_f:}
% \begin{syntax}
% |\foo_bar:f| \{ \meta{tokens} \cs{exp_stop_f:} \meta{more tokens} \}
% \end{syntax}
% This function terminates an \texttt{f}-type expansion. Thus if
% a function |\foo_bar:f| starts an \texttt{f}-type expansion
% and all of \meta{tokens} are expandable \cs{exp_stop_f:}
% terminates the expansion of tokens even if \meta{more tokens}
% are also expandable. The function itself is an implicit space
% token. Inside an \texttt{e}-type or \texttt{x}-type expansion, it retains its
% form, but when typeset it produces the underlying space (\verb*| |).
% \end{function}
%
%
% \section{Controlled expansion}
%
% The \pkg{expl3} language makes all efforts to hide the complexity of
% \TeX{} expansion from the programmer by providing concepts that
% evaluate/expand arguments of functions prior to calling the \enquote{base}
% functions. Thus, instead of using many \tn{expandafter} calls and
% other trickery it is usually a matter of choosing the right variant
% of a function to achieve a desired result.
%
% Of course, deep down \TeX{} is using expansion as always and there
% are cases where a programmer needs to control that expansion
% directly; typical situations are basic data manipulation tools. This
% section documents the functions for that level. These
% commands are used throughout the kernel code, but we hope that outside
% the kernel there will be little need to resort to them. Instead the
% argument manipulation methods document above should usually be sufficient.
%
% While \cs{exp_after:wN} expands one token (out of order) it is
% sometimes necessary to expand several tokens in one go. The next set
% of commands provide this functionality. Be aware that it is
% absolutely required that the programmer has full control over the
% tokens to be expanded, i.e., it is not possible to use these
% functions to expand unknown input as part of
% \meta{expandable-tokens} as that will break badly if unexpandable
% tokens are encountered in that place!
%
% \begin{function}[added=2015-08-23,EXP]
% {
% \exp:w ,
% \exp_end:
% }
% \begin{syntax}
% \cs{exp:w} \meta{expandable tokens} \cs{exp_end:} \\
% \end{syntax}
% Expands \meta{expandable-tokens} until reaching \cs{exp_end:} at
% which point expansion stops.
% The full expansion of \meta{expandable tokens} has to be empty.
% If any token in \meta{expandable tokens} or any token generated by
% expanding the tokens therein is not expandable the expansion will end
% prematurely and as a result \cs{exp_end:} will be misinterpreted
% later on.\footnotemark
%
% In typical use cases the \cs{exp_end:} is hidden somewhere
% in the replacement text of \meta{expandable-tokens} rather than
% being on the same expansion level than \cs{exp:w}, e.g., you may
% see code such as
%\begin{verbatim}
% \exp:w \@@_case:NnTF #1 {#2} { } { }
%\end{verbatim}
% where somewhere during the expansion of |\@@_case:NnTF| the
% \cs{exp_end:} gets generated.
% \begin{texnote}
% The current implementation uses \tn{romannumeral} hence ignores
% space tokens and explicit signs |+| and |-| in the expansion of the
% \meta{expandable tokens}, but this should not be relied upon.
% \end{texnote}
% \end{function}
% \footnotetext{Due to the implementation you might get the character
% in position 0 in the current font (typically \enquote{\texttt{`}})
% in the output without any error message!}
%
% \begin{function}[added=2015-08-23, EXP, label = \exp_end_continue_f:w]
% {
% \exp:w ,
% \exp_end_continue_f:w
% }
% \begin{syntax}
% \cs{exp:w} \meta{expandable-tokens} \cs{exp_end_continue_f:w} \meta{further-tokens}
% \end{syntax}
% Expands \meta{expandable-tokens} until reaching \cs{exp_end_continue_f:w} at
% which point expansion continues as an \texttt{f}-type expansion expanding
% \meta{further-tokens} until an unexpandable token is encountered (or
% the \texttt{f}-type expansion is explicitly terminated by
% \cs{exp_stop_f:}). As with all \texttt{f}-type expansions a space ending
% the expansion gets removed.
%
% The full expansion of \meta{expandable-tokens} has to be empty.
% If any token in \meta{expandable-tokens} or any token generated by
% expanding the tokens therein is not expandable the expansion will end
% prematurely and as a result \cs{exp_end_continue_f:w} will be misinterpreted
% later on.\footnotemark
%
%
% In typical use cases \meta{expandable-tokens} contains no tokens at all,
% e.g., you will see code such as
%\begin{verbatim}
% \exp_after:wN { \exp:w \exp_end_continue_f:w #2 }
%\end{verbatim}
% where the \cs{exp_after:wN} triggers an \texttt{f}-expansion of the tokens
% in |#2|. For technical reasons this has to happen using two tokens
% (if they would be hidden inside another command \cs{exp_after:wN}
% would only expand the command but not trigger any additional
% |f|-expansion).
%
% You might wonder why there are two different approaches available,
% after all the effect of
% \begin{quote}
% \cs{exp:w} \meta{expandable-tokens} \cs{exp_end:}
% \end{quote}
% can be alternatively achieved through an \texttt{f}-type expansion by using
% \cs{exp_stop_f:}, i.e.
% \begin{quote}
% \cs{exp:w} \cs{exp_end_continue_f:w} \meta{expandable-tokens} \cs{exp_stop_f:}
% \end{quote}
% The reason is simply that the first approach is slightly faster
% (one less token to parse and less expansion internally)
% so in places where such performance really matters and where we
% want to explicitly stop the expansion at a defined point the first
% form is preferable.
% \end{function}
% \footnotetext{In this particular case you may get a character into
% the output as well as an error message.}
%
% \begin{function}[added=2015-08-23, EXP, label = \exp_end_continue_f:nw]
% {
% \exp:w ,
% \exp_end_continue_f:nw
% }
% \begin{syntax}
% \cs{exp:w} \meta{expandable-tokens} \cs{exp_end_continue_f:nw} \meta{further-tokens}
% \end{syntax}
% The difference to \cs{exp_end_continue_f:w} is that we first we pick
% up an argument which is then returned to the input stream. If
% \meta{further-tokens} starts with space tokens then these space
% tokens are removed while searching for the argument. If it starts
% with a brace group then the braces are removed. Thus such spaces or
% braces will not terminate the \texttt{f}-type expansion.
% \end{function}
%
% \section{Internal functions}
%
% \begin{function}{\::n, \::N, \::p, \::c, \::o, \::e, \::f, \::x, \::v, \::V, \:::}
% \begin{syntax}
% |\cs_new:Npn \exp_args:Ncof { \::c \::o \::f \::: }|
% \end{syntax}
% Internal forms for the base expansion types. These names do \emph{not}
% conform to the general \LaTeX3 approach as this makes them more readily
% visible in the log and so forth. They should not be used outside this module.
% \end{function}
%
% \begin{function}
% {\::o_unbraced, \::e_unbraced, \::f_unbraced, \::x_unbraced, \::v_unbraced, \::V_unbraced}
% \begin{syntax}
% |\cs_new:Npn \exp_last_unbraced:Nno { \::n \::o_unbraced \::: }|
% \end{syntax}
% Internal forms for the expansion types which leave the terminal argument
% unbraced. These names do \emph{not}
% conform to the general \LaTeX3 approach as this makes them more readily
% visible in the log and so forth. They should not be used outside this module.
% \end{function}
%
% \end{documentation}
%
% \begin{implementation}
%
% \section{\pkg{l3expan} implementation}
%
% \begin{macrocode}
%<*package>
% \end{macrocode}
%
% \begin{macrocode}
%<@@=exp>
% \end{macrocode}
%
% \begin{variable}{\l_@@_internal_tl}
% The |\exp_| module has its private variable to temporarily store the
% result of |x|-type argument expansion. This is done to avoid interference
% with other functions using temporary variables.
% \end{variable}
%
% \begin{macro}{\exp_after:wN}
% \begin{macro}{\exp_not:N}
% \begin{macro}{\exp_not:n}
% These are defined in \pkg{l3basics}, as they are needed
% \enquote{early}. This is just a reminder of that fact!
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{General expansion}
%
% In this section a general mechanism for defining functions that handle
% arguments is defined. These general expansion functions are
% expandable unless |x| is used. (Any version of |x| is going to have
% to use one of the \LaTeX3 names for \cs{cs_set:Npx} at some
% point, and so is never going to be expandable.)
%
% The definition of expansion functions with this technique happens
% in section~\ref{sec:l3expan:gendef}.
% In section~\ref{sec:l3expan:handtune} some common cases are coded by a more direct
% method for efficiency, typically using calls to \cs{exp_after:wN}.
%
% \begin{variable}{\l_@@_internal_tl}
% This scratch token list variable is defined in \pkg{l3basics}.
% \end{variable}
%
% This code uses internal functions with names that start with |\::| to
% perform the expansions. All macros are |long| since the tokens
% undergoing expansion may be arbitrary user input.
%
% An argument manipulator |\::|\meta{Z} always has signature |#1\:::#2#3|
% where |#1| holds the remaining argument manipulations to be performed,
% \cs{:::} serves as an end marker for the list of manipulations, |#2|
% is the carried over result of the previous expansion steps and |#3| is
% the argument about to be processed.
% One exception to this rule is \cs{::p}, which has to grab an argument
% delimited by a left brace.
%
% \begin{macro}[EXP]{\@@_arg_next:nnn}
% \begin{macro}[EXP]{\@@_arg_next:Nnn}
% |#1| is the result of an expansion step, |#2| is the remaining
% argument manipulations and |#3| is the current result of the
% expansion chain. This auxiliary function moves |#1| back after
% |#3| in the input stream and checks if any expansion is left to
% be done by calling |#2|. In by far the most cases we need
% to add a set of braces to the result of an argument manipulation
% so it is more effective to do it directly here. Actually, so far
% only the |c| of the final argument manipulation variants does not
% require a set of braces.
% \begin{macrocode}
\cs_new:Npn \@@_arg_next:nnn #1#2#3 { #2 \::: { #3 {#1} } }
\cs_new:Npn \@@_arg_next:Nnn #1#2#3 { #2 \::: { #3 #1 } }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\:::}
% The end marker is just another name for the identity function.
% \begin{macrocode}
\cs_new:Npn \::: #1 {#1}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::n}
% This function is used to skip an argument that doesn't need to
% be expanded.
% \begin{macrocode}
\cs_new:Npn \::n #1 \::: #2#3 { #1 \::: { #2 {#3} } }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::N}
% This function is used to skip an argument that consists of a
% single token and doesn't need to be expanded.
% \begin{macrocode}
\cs_new:Npn \::N #1 \::: #2#3 { #1 \::: {#2#3} }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::p}
% This function is used to skip an argument that is delimited by a
% left brace and doesn't need to be expanded. It is not
% wrapped in braces in the result.
% \begin{macrocode}
\cs_new:Npn \::p #1 \::: #2#3# { #1 \::: {#2#3} }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::c}
% This function is used to skip an argument that is turned into
% a control sequence without expansion.
% \begin{macrocode}
\cs_new:Npn \::c #1 \::: #2#3
{ \exp_after:wN \@@_arg_next:Nnn \cs:w #3 \cs_end: {#1} {#2} }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::o}
% This function is used to expand an argument once.
% \begin{macrocode}
\cs_new:Npn \::o #1 \::: #2#3
{ \exp_after:wN \@@_arg_next:nnn \exp_after:wN {#3} {#1} {#2} }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::e}
% With the \tn{expanded} primitive available, just expand.
% \begin{macrocode}
\cs_new:Npn \::e #1 \::: #2#3
{ \tex_expanded:D { \exp_not:n { #1 \::: } { \exp_not:n {#2} {#3} } } }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::f}
% \begin{macro}{\exp_stop_f:}
% This function is used to expand a token list until the first
% unexpandable token is found. This is achieved through \cs{exp:w}
% \cs{exp_end_continue_f:w} that expands everything in its way
% following it. This scanning procedure is terminated once the
% expansion hits something non-expandable (if that is a space it is
% removed). We introduce \cs{exp_stop_f:} to mark such an
% end-of-expansion marker. For example, |f|-expanding
% |\cs_set_eq:Nc \aaa { b \l_tmpa_tl b }| where |\l_tmpa_tl| contains
% the characters |lur| gives |\tex_let:D \aaa = \blurb| which then
% turns out to start with the non-expandable token |\tex_let:D|.
% Since the expansion of \cs{exp:w} \cs{exp_end_continue_f:w} is
% empty, we wind up with a fully expanded list, only \TeX{} has not
% tried to execute any of the non-expandable tokens. This is what
% differentiates this function from the |e| and |x| argument type.
% \begin{macrocode}
\cs_new:Npn \::f #1 \::: #2#3
{
\exp_after:wN \@@_arg_next:nnn
\exp_after:wN { \exp:w \exp_end_continue_f:w #3 }
{#1} {#2}
}
\use:nn { \cs_new_eq:NN \exp_stop_f: } { ~ }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\::x}
% This function is used to expand an argument fully.
% We build in the expansion of \cs{@@_arg_next:nnn}.
% \begin{macrocode}
\cs_new_protected:Npn \::x #1 \::: #2#3
{
\cs_set_nopar:Npe \l_@@_internal_tl
{ \exp_not:n { #1 \::: } { \exp_not:n {#2} {#3} } }
\l_@@_internal_tl
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\::v}
% \begin{macro}[EXP]{\::V}
% These functions return the value of a register, i.e., one of
% |tl|, |clist|, |int|, |skip|, |dim|, |muskip|, or built-in
% \TeX{} register. The |V| version
% expects a single token whereas |v| like |c| creates a csname from
% its argument given in braces and then evaluates it as if it was a
% |V|. The \cs{exp:w} sets off an expansion
% similar to an |f|-type expansion, which we terminate using
% \cs{exp_end:}. The argument is returned in braces.
% \begin{macrocode}
\cs_new:Npn \::V #1 \::: #2#3
{
\exp_after:wN \@@_arg_next:nnn
\exp_after:wN { \exp:w \@@_eval_register:N #3 }
{#1} {#2}
}
\cs_new:Npn \::v #1 \::: #2#3
{
\exp_after:wN \@@_arg_next:nnn
\exp_after:wN { \exp:w \@@_eval_register:c {#3} }
{#1} {#2}
}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}[EXP]{\@@_eval_register:N, \@@_eval_register:c}
% \begin{macro}[EXP]{\@@_eval_error_msg:w}
% This function evaluates a register. Now a register might exist as
% one of two things: A parameter-less macro or a built-in \TeX{}
% register such as |\count|. For the \TeX{} registers we have to
% utilize a \tn{the} whereas for the macros we merely have to
% expand them once. The trick is to find out when to use
% \tn{the} and when not to. What we want here is to find out
% whether the token expands to something else when hit with
% \cs{exp_after:wN}. The technique is to compare the meaning of the
% token in question when it has been prefixed with \cs{exp_not:N}
% and the token itself. If it is a macro, the prefixed
% \cs{exp_not:N} temporarily turns it into the primitive
% \cs{scan_stop:}.
% \begin{macrocode}
\cs_new:Npn \@@_eval_register:N #1
{
\exp_after:wN \if_meaning:w \exp_not:N #1 #1
% \end{macrocode}
% If the token was not a macro it may be a malformed variable from a
% |c| expansion in which case it is equal to the primitive
% \cs{scan_stop:}. In that case we throw an error. We could let \TeX{}
% do it for us but that would result in the rather obscure
% \begin{quote}
% |! You can't use `\relax' after \the.|
% \end{quote}
% which while quite true doesn't give many hints as to what actually
% went wrong. We provide something more sensible.
% \begin{macrocode}
\if_meaning:w \scan_stop: #1
\@@_eval_error_msg:w
\fi:
% \end{macrocode}
% The next bit requires some explanation. The function must be
% initiated by \cs{exp:w} and we want to
% terminate this expansion chain by inserting the \cs{exp_end:}
% token.
% However, we have to expand the register |#1| before we do
% that. If it is a \TeX{} register, we need to execute the sequence
% |\exp_after:wN \exp_end: \tex_the:D #1| and if it is a macro we
% need to execute |\exp_after:wN \exp_end: #1|. We therefore issue
% the longer of the two sequences and if the register is a macro, we
% remove the \cs{tex_the:D}.
% \begin{macrocode}
\else:
\exp_after:wN \use_i_ii:nnn
\fi:
\exp_after:wN \exp_end: \tex_the:D #1
}
\cs_new:Npn \@@_eval_register:c #1
{ \exp_after:wN \@@_eval_register:N \cs:w #1 \cs_end: }
% \end{macrocode}
% Clean up nicely, then call the undefined control sequence. The
% result is an error message looking like this:
% \begin{verbatim}
% ! Undefined control sequence.
% \LaTeX3 error:
% Erroneous variable used!
% l.55 \tl_set:Nv \l_tmpa_tl {undefined_tl}
% \end{verbatim}
% \begin{macrocode}
\cs_new:Npn \@@_eval_error_msg:w #1 \tex_the:D #2
{
\fi:
\fi:
\msg_expandable_error:nnn { kernel } { bad-variable } {#2}
\exp_end:
}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \subsection{Hand-tuned definitions}
% \label{sec:l3expan:handtune}
%
% One of the most important features of these functions is that they
% are fully expandable.
%
% \begin{macro}[EXP]{\exp_args:Nc, \exp_args:cc}
% In \pkg{l3basics}.
% \end{macro}
%
% \begin{macro}[EXP]{\exp_args:NNc, \exp_args:Ncc, \exp_args:Nccc}
% Here are the functions that turn their argument into csnames but are
% expandable.
% \begin{macrocode}
\cs_new:Npn \exp_args:NNc #1#2#3
{ \exp_after:wN #1 \exp_after:wN #2 \cs:w # 3\cs_end: }
\cs_new:Npn \exp_args:Ncc #1#2#3
{ \exp_after:wN #1 \cs:w #2 \exp_after:wN \cs_end: \cs:w #3 \cs_end: }
\cs_new:Npn \exp_args:Nccc #1#2#3#4
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\cs:w #3 \exp_after:wN \cs_end:
\cs:w #4 \cs_end:
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\exp_args:No}
% \begin{macro}[EXP]{\exp_args:NNo}
% \begin{macro}[EXP]{\exp_args:NNNo}
% Those lovely runs of expansion!
% \begin{macrocode}
\cs_new:Npn \exp_args:No #1#2 { \exp_after:wN #1 \exp_after:wN {#2} }
\cs_new:Npn \exp_args:NNo #1#2#3
{ \exp_after:wN #1 \exp_after:wN #2 \exp_after:wN {#3} }
\cs_new:Npn \exp_args:NNNo #1#2#3#4
{ \exp_after:wN #1 \exp_after:wN#2 \exp_after:wN #3 \exp_after:wN {#4} }
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}[EXP]{\exp_args:Ne}
% When the \tn{expanded} primitive is available, use it.
% \begin{macrocode}
\cs_new:Npn \exp_args:Ne #1#2
{ \exp_after:wN #1 \tex_expanded:D { {#2} } }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\exp_args:Nf, \exp_args:NV, \exp_args:Nv}
% \begin{macrocode}
\cs_new:Npn \exp_args:Nf #1#2
{ \exp_after:wN #1 \exp_after:wN { \exp:w \exp_end_continue_f:w #2 } }
\cs_new:Npn \exp_args:Nv #1#2
{
\exp_after:wN #1 \exp_after:wN
{ \exp:w \@@_eval_register:c {#2} }
}
\cs_new:Npn \exp_args:NV #1#2
{
\exp_after:wN #1 \exp_after:wN
{ \exp:w \@@_eval_register:N #2 }
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]
% {
% \exp_args:NNV, \exp_args:NNv, \exp_args:NNe, \exp_args:NNf,
% \exp_args:Nco, \exp_args:NcV, \exp_args:Ncv, \exp_args:Ncf,
% \exp_args:NVV,
% }
% Some more hand-tuned function with three arguments.
% If we forced that an |o| argument always has braces,
% we could implement \cs{exp_args:Nco} with less tokens
% and only two arguments.
% \begin{macrocode}
\cs_new:Npn \exp_args:NNV #1#2#3
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN { \exp:w \@@_eval_register:N #3 }
}
\cs_new:Npn \exp_args:NNv #1#2#3
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN { \exp:w \@@_eval_register:c {#3} }
}
\cs_new:Npn \exp_args:NNe #1#2#3
{
\exp_after:wN #1
\exp_after:wN #2
\tex_expanded:D { {#3} }
}
\cs_new:Npn \exp_args:NNf #1#2#3
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN { \exp:w \exp_end_continue_f:w #3 }
}
\cs_new:Npn \exp_args:Nco #1#2#3
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\exp_after:wN {#3}
}
\cs_new:Npn \exp_args:NcV #1#2#3
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\exp_after:wN { \exp:w \@@_eval_register:N #3 }
}
\cs_new:Npn \exp_args:Ncv #1#2#3
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\exp_after:wN { \exp:w \@@_eval_register:c {#3} }
}
\cs_new:Npn \exp_args:Ncf #1#2#3
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\exp_after:wN { \exp:w \exp_end_continue_f:w #3 }
}
\cs_new:Npn \exp_args:NVV #1#2#3
{
\exp_after:wN #1
\exp_after:wN { \exp:w \exp_after:wN
\@@_eval_register:N \exp_after:wN #2 \exp_after:wN }
\exp_after:wN { \exp:w \@@_eval_register:N #3 }
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]
% {
% \exp_args:NNNV, \exp_args:NNNv, \exp_args:NNNe,
% \exp_args:NcNc, \exp_args:NcNo,
% \exp_args:Ncco,
% }
% A few more that we can hand-tune.
% \begin{macrocode}
\cs_new:Npn \exp_args:NNNV #1#2#3#4
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN #3
\exp_after:wN { \exp:w \@@_eval_register:N #4 }
}
\cs_new:Npn \exp_args:NNNv #1#2#3#4
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN #3
\exp_after:wN { \exp:w \@@_eval_register:c {#4} }
}
\cs_new:Npn \exp_args:NNNe #1#2#3#4
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN #3
\tex_expanded:D { {#4} }
}
\cs_new:Npn \exp_args:NcNc #1#2#3#4
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\exp_after:wN #3
\cs:w #4 \cs_end:
}
\cs_new:Npn \exp_args:NcNo #1#2#3#4
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\exp_after:wN #3
\exp_after:wN {#4}
}
\cs_new:Npn \exp_args:Ncco #1#2#3#4
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\cs:w #3 \exp_after:wN \cs_end:
\exp_after:wN {#4}
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\exp_args:Nx}
% \begin{macrocode}
\cs_new_protected:Npn \exp_args:Nx #1#2
{ \use:x { \exp_not:N #1 {#2} } }
% \end{macrocode}
% \end{macro}
%
% \subsection{Last-unbraced versions}
%
% \begin{macro}[EXP]{\@@_arg_last_unbraced:nn}
% \begin{macro}[EXP]{\::o_unbraced}
% \begin{macro}[EXP]{\::V_unbraced}
% \begin{macro}[EXP]{\::v_unbraced}
% \begin{macro}[EXP]{\::e_unbraced}
% \begin{macro}[EXP]{\::f_unbraced}
% \begin{macro}[EXP]{\::x_unbraced}
% There are a few places where the last argument needs to be available
% unbraced. First some helper macros.
% \begin{macrocode}
\cs_new:Npn \@@_arg_last_unbraced:nn #1#2 { #2#1 }
\cs_new:Npn \::o_unbraced \::: #1#2
{ \exp_after:wN \@@_arg_last_unbraced:nn \exp_after:wN {#2} {#1} }
\cs_new:Npn \::V_unbraced \::: #1#2
{
\exp_after:wN \@@_arg_last_unbraced:nn
\exp_after:wN { \exp:w \@@_eval_register:N #2 } {#1}
}
\cs_new:Npn \::v_unbraced \::: #1#2
{
\exp_after:wN \@@_arg_last_unbraced:nn
\exp_after:wN { \exp:w \@@_eval_register:c {#2} } {#1}
}
\cs_new:Npn \::e_unbraced \::: #1#2
{ \tex_expanded:D { \exp_not:n {#1} #2 } }
\cs_new:Npn \::f_unbraced \::: #1#2
{
\exp_after:wN \@@_arg_last_unbraced:nn
\exp_after:wN { \exp:w \exp_end_continue_f:w #2 } {#1}
}
\cs_new_protected:Npn \::x_unbraced \::: #1#2
{
\cs_set_nopar:Npe \l_@@_internal_tl { \exp_not:n {#1} #2 }
\l_@@_internal_tl
}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}[EXP]
% {
% \exp_last_unbraced:No,
% \exp_last_unbraced:NV,
% \exp_last_unbraced:Nv,
% \exp_last_unbraced:Ne,
% \exp_last_unbraced:Nf,
% \exp_last_unbraced:NNo,
% \exp_last_unbraced:NNV,
% \exp_last_unbraced:NNf,
% \exp_last_unbraced:Nco,
% \exp_last_unbraced:NcV,
% \exp_last_unbraced:NNNo,
% \exp_last_unbraced:NNNV,
% \exp_last_unbraced:NNNf,
% \exp_last_unbraced:Nno,
% \exp_last_unbraced:Nnf,
% \exp_last_unbraced:Noo,
% \exp_last_unbraced:Nfo,
% \exp_last_unbraced:NnNo,
% \exp_last_unbraced:NNNNo,
% \exp_last_unbraced:NNNNf,
% }
% \begin{macro}{\exp_last_unbraced:Nx}
% Now the business end: most of these are hand-tuned for speed, but the
% general system is in place.
% \begin{macrocode}
\cs_new:Npn \exp_last_unbraced:No #1#2 { \exp_after:wN #1 #2 }
\cs_new:Npn \exp_last_unbraced:NV #1#2
{ \exp_after:wN #1 \exp:w \@@_eval_register:N #2 }
\cs_new:Npn \exp_last_unbraced:Nv #1#2
{ \exp_after:wN #1 \exp:w \@@_eval_register:c {#2} }
\cs_new:Npn \exp_last_unbraced:Ne #1#2
{ \exp_after:wN #1 \tex_expanded:D {#2} }
\cs_new:Npn \exp_last_unbraced:Nf #1#2
{ \exp_after:wN #1 \exp:w \exp_end_continue_f:w #2 }
\cs_new:Npn \exp_last_unbraced:NNo #1#2#3
{ \exp_after:wN #1 \exp_after:wN #2 #3 }
\cs_new:Npn \exp_last_unbraced:NNV #1#2#3
{
\exp_after:wN #1
\exp_after:wN #2
\exp:w \@@_eval_register:N #3
}
\cs_new:Npn \exp_last_unbraced:NNf #1#2#3
{
\exp_after:wN #1
\exp_after:wN #2
\exp:w \exp_end_continue_f:w #3
}
\cs_new:Npn \exp_last_unbraced:Nco #1#2#3
{ \exp_after:wN #1 \cs:w #2 \exp_after:wN \cs_end: #3 }
\cs_new:Npn \exp_last_unbraced:NcV #1#2#3
{
\exp_after:wN #1
\cs:w #2 \exp_after:wN \cs_end:
\exp:w \@@_eval_register:N #3
}
\cs_new:Npn \exp_last_unbraced:NNNo #1#2#3#4
{ \exp_after:wN #1 \exp_after:wN #2 \exp_after:wN #3 #4 }
\cs_new:Npn \exp_last_unbraced:NNNV #1#2#3#4
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN #3
\exp:w \@@_eval_register:N #4
}
\cs_new:Npn \exp_last_unbraced:NNNf #1#2#3#4
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN #3
\exp:w \exp_end_continue_f:w #4
}
\cs_new:Npn \exp_last_unbraced:Nno { \::n \::o_unbraced \::: }
\cs_new:Npn \exp_last_unbraced:Nnf { \::n \::f_unbraced \::: }
\cs_new:Npn \exp_last_unbraced:Noo { \::o \::o_unbraced \::: }
\cs_new:Npn \exp_last_unbraced:Nfo { \::f \::o_unbraced \::: }
\cs_new:Npn \exp_last_unbraced:NnNo { \::n \::N \::o_unbraced \::: }
\cs_new:Npn \exp_last_unbraced:NNNNo #1#2#3#4#5
{ \exp_after:wN #1 \exp_after:wN #2 \exp_after:wN #3 \exp_after:wN #4 #5 }
\cs_new:Npn \exp_last_unbraced:NNNNf #1#2#3#4#5
{
\exp_after:wN #1
\exp_after:wN #2
\exp_after:wN #3
\exp_after:wN #4
\exp:w \exp_end_continue_f:w #5
}
\cs_new_protected:Npn \exp_last_unbraced:Nx { \::x_unbraced \::: }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}[EXP]{\exp_last_two_unbraced:Noo}
% \begin{macro}[EXP]{\@@_last_two_unbraced:noN}
% If |#2| is a single token then this can be implemented as
% \begin{verbatim}
% \cs_new:Npn \exp_last_two_unbraced:Noo #1 #2 #3
% { \exp_after:wN \exp_after:wN \exp_after:wN #1 \exp_after:wN #2 #3 }
% \end{verbatim}
% However, for robustness this is not suitable. Instead, a bit of a
% shuffle is used to ensure that |#2| can be multiple tokens.
% \begin{macrocode}
\cs_new:Npn \exp_last_two_unbraced:Noo #1#2#3
{ \exp_after:wN \@@_last_two_unbraced:noN \exp_after:wN {#3} {#2} #1 }
\cs_new:Npn \@@_last_two_unbraced:noN #1#2#3
{ \exp_after:wN #3 #2 #1 }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \subsection{Preventing expansion}
%
% \begin{macro}{\__kernel_exp_not:w}
% At the kernel level, we need the primitive behaviour to allow expansion
% \emph{before} the brace group.
% \begin{macrocode}
\cs_new_eq:NN \__kernel_exp_not:w \tex_unexpanded:D
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[EXP]{\exp_not:c}
% \begin{macro}[EXP]{\exp_not:o}
% \begin{macro}[EXP]{\exp_not:e}
% \begin{macro}[EXP]{\exp_not:f}
% \begin{macro}[EXP]{\exp_not:V}
% \begin{macro}[EXP]{\exp_not:v}
% All these except \cs{exp_not:c} call the kernel-internal
% \cs{__kernel_exp_not:w} namely \cs{tex_unexpanded:D}.
% \begin{macrocode}
\cs_new:Npn \exp_not:c #1 { \exp_after:wN \exp_not:N \cs:w #1 \cs_end: }
\cs_new:Npn \exp_not:o #1 { \__kernel_exp_not:w \exp_after:wN {#1} }
\cs_new:Npn \exp_not:e #1
{ \__kernel_exp_not:w \tex_expanded:D { {#1} } }
\cs_new:Npn \exp_not:f #1
{ \__kernel_exp_not:w \exp_after:wN { \exp:w \exp_end_continue_f:w #1 } }
\cs_new:Npn \exp_not:V #1
{
\__kernel_exp_not:w \exp_after:wN
{ \exp:w \@@_eval_register:N #1 }
}
\cs_new:Npn \exp_not:v #1
{
\__kernel_exp_not:w \exp_after:wN
{ \exp:w \@@_eval_register:c {#1} }
}
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{Controlled expansion}
%
% \begin{macro}{\exp:w}
% \begin{macro}{\exp_end:}
% \begin{macro}{\exp_end_continue_f:w}
% \begin{macro}{\exp_end_continue_f:nw}
% To trigger a sequence of \enquote{arbitrarily} many expansions we
% need a method to invoke \TeX's expansion mechanism in such a way
% that (a) we are able to stop it in a controlled manner and (b) the
% result of what triggered the expansion in the first place is null,
% i.e.\@, that we do not get any unwanted side effects. There aren't
% that many possibilities in \TeX{}; in fact the one explained below
% might well be the only one (as normally the result of expansion is
% not null).
%
% The trick here is to make use of the fact that
% \cs{tex_romannumeral:D} expands the tokens following it when looking
% for a number and that its expansion is null if that number turns out
% to be zero or negative. So we use that to start the expansion
% sequence: \cs{exp:w} is set equal to \cs{tex_romannumeral:D} in
% \pkg{l3basics}. To stop the expansion sequence in a controlled way
% all we need to provide is a constant integer zero as part of
% expanded tokens. As this is an integer constant it immediately stops
% \cs{tex_romannumeral:D}'s search for a number. Again, the
% definition of \cs{exp_end:} as the integer constant zero is in
% \pkg{l3basics}. (Note that according to our specification all
% tokens we expand initiated by \cs{exp:w} are supposed to be
% expandable (as well as their replacement text in the expansion) so
% we will not encounter a \enquote{number} that actually result in a
% roman numeral being generated. Or if we do then the programmer made
% a mistake.)
%
% If on the other hand we want to stop the initial expansion sequence
% but continue with an \texttt{f}-type expansion we provide the
% alphabetic constant |`^^@| that also represents |0| but this time
% \TeX's syntax for a \meta{number} continues searching for an
% optional space (and it continues expansion doing that) --- see
% \TeX{}book page~269 for details.
% \begin{macrocode}
\group_begin:
\tex_catcode:D `\^^@ = 13
\cs_new_protected:Npn \exp_end_continue_f:w { `^^@ }
% \end{macrocode}
% If the above definition ever appears outside its proper context
% the active character |^^@| will be executed so we turn this into an
% error. The test for existence covers the (unlikely) case that some
% other code has already defined |^^@|: this is true for example for
% \texttt{xmltex.tex}.
% \begin{macrocode}
\if_cs_exist:N ^^@
\else:
\cs_new:Npn ^^@
{ \msg_expandable_error:nn { kernel } { bad-exp-end-f } }
\fi:
% \end{macrocode}
% The same but grabbing an argument to remove spaces and braces.
% \begin{macrocode}
\cs_new:Npn \exp_end_continue_f:nw #1 { `^^@ #1 }
\group_end:
% \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \subsection{Defining function variants}
%
% \begin{macrocode}
%<@@=cs>
% \end{macrocode}
%
% \begin{variable}{\s_@@_mark,\s_@@_stop}
% Internal scan marks. No \pkg{l3quark} yet, so do things by hand.
% \begin{macrocode}
\cs_new_eq:NN \s_@@_mark \scan_stop:
\cs_new_eq:NN \s_@@_stop \scan_stop:
% \end{macrocode}
% \end{variable}
%
% \begin{variable}{\q_@@_recursion_stop}
% Internal recursion quarks. No \pkg{l3quark} yet, so do things by hand.
% \begin{macrocode}
\cs_new:Npn \q_@@_recursion_stop { \q_@@_recursion_stop }
% \end{macrocode}
% \end{variable}
%
% \begin{macro}[EXP]{
% \@@_use_none_delimit_by_s_stop:w,
% \@@_use_i_delimit_by_s_stop:nw,
% \@@_use_none_delimit_by_q_recursion_stop:w
% }
% Internal scan marks.
% \begin{macrocode}
\cs_new:Npn \@@_use_none_delimit_by_s_stop:w #1 \s_@@_stop { }
\cs_new:Npn \@@_use_i_delimit_by_s_stop:nw #1 #2 \s_@@_stop {#1}
\cs_new:Npn \@@_use_none_delimit_by_q_recursion_stop:w
#1 \q_@@_recursion_stop { }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\cs_generate_variant:Nn, \cs_generate_variant:cn}
% \begin{arguments}
% \item Base form of a function; \emph{e.g.},~\cs{tl_set:Nn}
% \item One or more variant argument specifiers; e.g., |{Nx,c,cx}|
% \end{arguments}
% After making sure that the base form exists, test whether it is
% protected or not and define \cs{@@_tmp:w} as either
% \cs{cs_new:Npe} or \cs{cs_new_protected:Npe}, which is
% then used to define all the variants (except those involving
% \texttt{x}-expansion, always protected). Split up the original base
% function only once, to grab its name and signature. Then we wish to
% iterate through the comma list of variant argument specifiers, which
% we first convert to a string: the reason is explained later.
% \begin{macrocode}
\cs_new_protected:Npn \cs_generate_variant:Nn #1#2
{
\@@_generate_variant:N #1
\use:e
{
\@@_generate_variant:nnNN
\cs_split_function:N #1
\exp_not:N #1
\tl_to_str:n {#2} ,
\exp_not:N \scan_stop: ,
\exp_not:N \q_@@_recursion_stop
}
}
\cs_new_protected:Npn \cs_generate_variant:cn
{ \exp_args:Nc \cs_generate_variant:Nn }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_generate_variant:N}
% \begin{macro}{\@@_generate_variant:ww, \@@_generate_variant:wwNw}
% The goal here is to pick up protected parent functions. There are
% four cases: the parent function can be a primitive or a macro, and
% can be expandable or not. For non-expandable primitives, all
% variants should be protected; skipping the \cs{else:} branch is safe
% because non-expandable primitives cannot be \TeX{} conditionals.
%
% The other case where variants should be protected is when the parent
% function is a protected macro: then |protected| appears in the
% meaning before the first occurrence of |macro|. The |ww| auxiliary
% removes everything in the meaning string after the first |ma|. We
% use |ma| rather than the full |macro| because the meaning of the
% \tn{firstmark} primitive (and four others) can contain an arbitrary
% string after a leading |firstmark:|. Then, look for |pr| in the
% part we extracted: no need to look for anything longer: the only
% strings we can have are an empty string, \verb*|\long |,
% \verb*|\protected |, \verb*|\protected\long |, |\first|, |\top|,
% |\bot|, |\splittop|, or |\splitbot|, with |\| replaced by the
% appropriate escape character. If |pr| appears in the part before
% |ma|, the first \cs{s_@@_mark} is taken as an argument of the |wwNw|
% auxiliary, and |#3| is \cs{cs_new_protected:Npe}, otherwise it
% is \cs{cs_new:Npe}.
% \begin{macrocode}
\cs_new_protected:Npe \@@_generate_variant:N #1
{
\exp_not:N \exp_after:wN \exp_not:N \if_meaning:w
\exp_not:N \exp_not:N #1 #1
\cs_set_eq:NN \exp_not:N \@@_tmp:w \cs_new_protected:Npe
\exp_not:N \else:
\exp_not:N \exp_after:wN \exp_not:N \@@_generate_variant:ww
\exp_not:N \token_to_meaning:N #1 \tl_to_str:n { ma }
\s_@@_mark
\s_@@_mark \cs_new_protected:Npe
\tl_to_str:n { pr }
\s_@@_mark \cs_new:Npe
\s_@@_stop
\exp_not:N \fi:
}
\exp_last_unbraced:NNNNo
\cs_new_protected:Npn \@@_generate_variant:ww
#1 { \tl_to_str:n { ma } } #2 \s_@@_mark
{ \@@_generate_variant:wwNw #1 }
\exp_last_unbraced:NNNNo
\cs_new_protected:Npn \@@_generate_variant:wwNw
#1 { \tl_to_str:n { pr } } #2 \s_@@_mark #3 #4 \s_@@_stop
{ \cs_set_eq:NN \@@_tmp:w #3 }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\@@_generate_variant:nnNN}
% \begin{arguments}
% \item Base name.
% \item Base signature.
% \item Boolean.
% \item Base function.
% \end{arguments}
% If the boolean is \cs{c_false_bool}, the base function has no colon
% and we abort with an error; otherwise, set off a loop through the
% desired variant forms. The original function is retained as |#4| for
% efficiency.
% \begin{macrocode}
\cs_new_protected:Npn \@@_generate_variant:nnNN #1#2#3#4
{
\if_meaning:w \c_false_bool #3
\msg_error:nne { kernel } { missing-colon }
{ \token_to_str:c {#1} }
\exp_after:wN \@@_use_none_delimit_by_q_recursion_stop:w
\fi:
\@@_generate_variant:Nnnw #4 {#1}{#2}
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_generate_variant:Nnnw}
% \begin{arguments}
% \item Base function.
% \item Base name.
% \item Base signature.
% \item Beginning of variant signature.
% \end{arguments}
% First check whether to terminate the loop over variant forms. Then,
% for each variant form, construct a new function name using the
% original base name, the variant signature consisting of $l$ letters
% and the last $k-l$ letters of the base signature (of length $k$).
% For example, for a base function \cs{prop_put:Nnn} which needs a
% |cV| variant form, we want the new signature to be |cVn|.
%
% There are further subtleties:
% \begin{itemize}
% \item In \cs{cs_generate_variant:Nn} |\foo:nnTF| |{xxTF}|, we must define
% |\foo:xxTF| using |\exp_args:Nxx|,
% rather than a hypothetical |\exp_args:NxxTF|. Thus, we wish to
% trim a common trailing part from the base signature and the
% variant signature.
% \item In \cs{cs_generate_variant:Nn} |\foo:on| |{ox}|, the
% function |\foo:ox| must be defined using |\exp_args:Nnx|, not
% |\exp_args:Nox|, to avoid double |o| expansion.
% \item Lastly, \cs{cs_generate_variant:Nn} |\foo:on| |{xn}| must
% trigger an error, because we do not have a means to replace
% |o|-expansion by |x|-expansion.
% More generally, we can only convert |N| to |c|, or convert |n|
% to |V|, |v|, |o|, |e|, |f|, or |x|.
% \end{itemize}
% All this boils down to a few rules. Only |n| and |N|-type
% arguments can be replaced by \cs{cs_generate_variant:Nn}. Other
% argument types are allowed to be passed unchanged from the base
% form to the variant: in the process they are changed to |n|
% except for |N| and |p|-type arguments. A common trailing
% part is ignored.
%
% We compare the base and variant signatures one character at a time
% within |e|-expansion. The result is given to
% \cs{@@_generate_variant:wwNN} (defined later) in the form
% \meta{processed variant signature} \cs{s_@@_mark} \meta{errors}
% \cs{s_@@_stop} \meta{base function} \meta{new function}. If all went
% well, \meta{errors} is empty; otherwise, it is a kernel error
% message and some clean-up code.
%
% Note the space after |#3| and after the following brace group.
% Those are ignored by \TeX{} when fetching the last argument for
% \cs{@@_generate_variant_loop:nNwN}, but can be used as a delimiter
% for \cs{@@_generate_variant_loop_end:nwwwNNnn}.
% \begin{macrocode}
\cs_new_protected:Npn \@@_generate_variant:Nnnw #1#2#3#4 ,
{
\if_meaning:w \scan_stop: #4
\exp_after:wN \@@_use_none_delimit_by_q_recursion_stop:w
\fi:
\use:e
{
\exp_not:N \@@_generate_variant:wwNN
\@@_generate_variant_loop:nNwN { }
#4
\@@_generate_variant_loop_end:nwwwNNnn
\s_@@_mark
#3 ~
{ ~ { } \fi: \@@_generate_variant_loop_long:wNNnn } ~
{ }
\s_@@_stop
\exp_not:N #1 {#2} {#4}
}
\@@_generate_variant:Nnnw #1 {#2} {#3}
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[rEXP]
% {
% \@@_generate_variant_loop:nNwN,
% \@@_generate_variant_loop_base:N,
% \@@_generate_variant_loop_same:w,
% \@@_generate_variant_loop_end:nwwwNNnn,
% \@@_generate_variant_loop_long:wNNnn,
% \@@_generate_variant_loop_invalid:NNwNNnn,
% \@@_generate_variant_loop_special:NNwNNnn
% }
% \begin{arguments}
% \item Last few consecutive letters common between the base and
% variant (more precisely, \cs{@@_generate_variant_same:N}
% \meta{letter} for each letter).
% \item Next variant letter.
% \item Remainder of variant form.
% \item Next base letter.
% \end{arguments}
% The first argument is populated by
% \cs{@@_generate_variant_loop_same:w} when a variant letter and a
% base letter match. It is flushed into the input stream whenever the
% two letters are different: if the loop ends before, the argument is
% dropped, which means that trailing common letters are ignored.
%
% The case where the two letters are different is only allowed if the
% base is |N| and the variant is |c|, or when the base is |n| and the
% variant is |V|, |v|, |o|, |e|, |f|, or |x|. Otherwise, call
% \cs{@@_generate_variant_loop_invalid:NNwNNnn} to remove the end of
% the loop, get arguments at the end of the loop, and place an
% appropriate error message as a second argument of
% \cs{@@_generate_variant:wwNN}. If the letters are distinct and the
% base letter is indeed |n| or |N|, leave in the input stream whatever
% argument |#1| was collected, and the next variant letter |#2|, then
% loop by calling \cs{@@_generate_variant_loop:nNwN}.
%
% The loop can stop in three ways.
% \begin{itemize}
% \item If the end of the variant form is encountered first, |#2| is
% \cs{@@_generate_variant_loop_end:nwwwNNnn} (expanded by the
% conditional \cs{if:w}), which inserts some tokens to end the
% conditional; grabs the \meta{base name} as |#7|, the
% \meta{variant signature} |#8|, the \meta{next base letter} |#1|
% and the part |#3| of the base signature that wasn't read yet;
% and combines those into the \meta{new function} to be defined.
% \item If the end of the base form is encountered first, |#4| is
% |~{}\fi:| which ends the conditional (with an empty expansion),
% followed by \cs{@@_generate_variant_loop_long:wNNnn}, which
% places an error as the second argument of
% \cs{@@_generate_variant:wwNN}.
% \item The loop can be interrupted early if the requested expansion
% is unavailable, namely when the variant and base letters differ
% and the base is not the right one (|n| or |N| to support the
% variant). In that case too an error is placed as the second
% argument of \cs{@@_generate_variant:wwNN}.
% \end{itemize}
% Note that if the variant form has the same length as the base form,
% |#2| is as described in the first point, and |#4| as described in
% the second point above. The \cs{@@_generate_variant_loop_end:nwwwNNnn}
% breaking function takes the empty brace group in |#4| as its first
% argument: this empty brace group produces the correct signature for
% the full variant.
% \begin{macrocode}
\cs_new:Npn \@@_generate_variant_loop:nNwN #1#2#3 \s_@@_mark #4
{
\if:w #2 #4
\exp_after:wN \@@_generate_variant_loop_same:w
\else:
\if:w #4 \@@_generate_variant_loop_base:N #2 \else:
\if:w 0
\if:w N #4 \else: \if:w n #4 \else: 1 \fi: \fi:
\if:w \scan_stop: \@@_generate_variant_loop_base:N #2 1 \fi:
0
\@@_generate_variant_loop_special:NNwNNnn #4#2
\else:
\@@_generate_variant_loop_invalid:NNwNNnn #4#2
\fi:
\fi:
\fi:
#1
\prg_do_nothing:
#2
\@@_generate_variant_loop:nNwN { } #3 \s_@@_mark
}
\cs_new:Npn \@@_generate_variant_loop_base:N #1
{
\if:w c #1 N \else:
\if:w o #1 n \else:
\if:w V #1 n \else:
\if:w v #1 n \else:
\if:w f #1 n \else:
\if:w e #1 n \else:
\if:w x #1 n \else:
\if:w n #1 n \else:
\if:w N #1 N \else:
\scan_stop:
\fi:
\fi:
\fi:
\fi:
\fi:
\fi:
\fi:
\fi:
\fi:
}
\cs_new:Npn \@@_generate_variant_loop_same:w
#1 \prg_do_nothing: #2#3#4
{ #3 { #1 \@@_generate_variant_same:N #2 } }
\cs_new:Npn \@@_generate_variant_loop_end:nwwwNNnn
#1#2 \s_@@_mark #3 ~ #4 \s_@@_stop #5#6#7#8
{
\scan_stop: \scan_stop: \fi:
\s_@@_mark \s_@@_stop
\exp_not:N #6
\exp_not:c { #7 : #8 #1 #3 }
}
\cs_new:Npn \@@_generate_variant_loop_long:wNNnn #1 \s_@@_stop #2#3#4#5
{
\exp_not:n
{
\s_@@_mark
\msg_error:nnee { kernel } { variant-too-long }
{#5} { \token_to_str:N #3 }
\use_none:nnn
\s_@@_stop
#3
#3
}
}
\cs_new:Npn \@@_generate_variant_loop_invalid:NNwNNnn
#1#2 \fi: \fi: \fi: #3 \s_@@_stop #4#5#6#7
{
\fi: \fi: \fi:
\exp_not:n
{
\s_@@_mark
\msg_error:nneeee { kernel } { invalid-variant }
{#7} { \token_to_str:N #5 } {#1} {#2}
\use_none:nnn
\s_@@_stop
#5
#5
}
}
\cs_new:Npn \@@_generate_variant_loop_special:NNwNNnn
#1#2#3 \s_@@_stop #4#5#6#7
{
#3 \s_@@_stop #4 #5 {#6} {#7}
\exp_not:n
{
\msg_error:nneeee
{ kernel } { deprecated-variant }
{#7} { \token_to_str:N #5 } {#1} {#2}
}
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}[rEXP]{\@@_generate_variant_same:N}
% When the base and variant letters are identical, don't do any
% expansion. For most argument types, we can use the |n|-type
% no-expansion, but the |N| and |p| types require a slightly different
% behaviour with respect to braces. For |V|-type this function could
% output |N| to avoid adding useless braces but that is not a problem.
% \begin{macrocode}
\cs_new:Npn \@@_generate_variant_same:N #1
{
\if:w N #1 #1 \else:
\if:w p #1 #1 \else:
\token_to_str:N n
\if:w n #1 \else:
\@@_generate_variant_loop_special:NNwNNnn #1#1
\fi:
\fi:
\fi:
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_generate_variant:wwNN}
% If the variant form has already been defined, log its existence
% (provided \texttt{log-functions} is active).
% Otherwise, make sure that the |\exp_args:N #3| form is defined, and
% if it contains |x|, change \cs{@@_tmp:w} locally to
% \cs{cs_new_protected:Npe}. Then define the variant by
% combining the |\exp_args:N #3| variant and the base function.
% \begin{macrocode}
\cs_new_protected:Npn \@@_generate_variant:wwNN
#1 \s_@@_mark #2 \s_@@_stop #3#4
{
#2
\cs_if_free:NT #4
{
\group_begin:
\@@_generate_internal_variant:n {#1}
\@@_tmp:w #4 { \exp_not:c { exp_args:N #1 } \exp_not:N #3 }
\group_end:
}
}
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\@@_generate_internal_variant:n}
% \begin{macro}[rEXP]{\@@_generate_internal_variant_loop:n}
% First test for the presence of |x| (this is where working with
% strings makes our lives easier), as the result should be protected,
% and the next variant to be defined using that internal variant
% should be protected (done by setting \cs{@@_tmp:w}). Then call
% \cs{@@_generate_internal_variant:NNn} with arguments
% \cs{cs_new_protected:cpn} \cs{use:x} (for protected) or
% \cs{cs_new:cpn} \cs{tex_expanded:D} (expandable) and the signature. If |p|
% appears in the signature, or if the function to be defined is
% expandable and the primitive \tn{expanded} is not available, or if there
% are more than $8$ arguments, call
% some fall-back code that just puts the appropriate |\::| commands.
% Otherwise, call \cs{@@_generate_internal_one_go:NNn} to construct
% the \cs[no-index]{exp_args:N\dots} function as a macro taking up to
% $9$~arguments and expanding them using \cs{use:x} or \cs{tex_expanded:D}.
% \begin{macrocode}
\cs_new_protected:Npe \@@_generate_internal_variant:n #1
{
\exp_not:N \@@_generate_internal_variant:wwnNwn
#1 \s_@@_mark
{ \cs_set_eq:NN \exp_not:N \@@_tmp:w \cs_new_protected:Npe }
\cs_new_protected:cpn
\use:x
\token_to_str:N x \s_@@_mark
{ }
\cs_new:cpn
\exp_not:N \tex_expanded:D
\s_@@_stop
{#1}
}
\exp_last_unbraced:NNNNo
\cs_new_protected:Npn \@@_generate_internal_variant:wwnNwn #1
{ \token_to_str:N x } #2 \s_@@_mark #3#4#5#6 \s_@@_stop #7
{
#3
\cs_if_free:cT { exp_args:N #7 }
{ \@@_generate_internal_variant:NNn #4 #5 {#7} }
}
\cs_set_protected:Npn \@@_tmp:w #1
{
\cs_new_protected:Npn \@@_generate_internal_variant:NNn ##1##2##3
{
\if_catcode:w X \use_none:nnnnnnnn ##3
\prg_do_nothing: \prg_do_nothing: \prg_do_nothing:
\prg_do_nothing: \prg_do_nothing: \prg_do_nothing:
\prg_do_nothing: \prg_do_nothing: X
\exp_after:wN \@@_generate_internal_test:Nw \exp_after:wN ##2
\else:
\exp_after:wN \@@_generate_internal_test_aux:w \exp_after:wN #1
\fi:
##3
\s_@@_mark
{
\use:e
{
##1 { exp_args:N ##3 }
{ \@@_generate_internal_variant_loop:n ##3 { : \use_i:nn } }
}
}
#1
\s_@@_mark
{ \exp_not:n { \@@_generate_internal_one_go:NNn ##1 ##2 {##3} } }
\s_@@_stop
}
\cs_new_protected:Npn \@@_generate_internal_test_aux:w
##1 #1 ##2 \s_@@_mark ##3 ##4 \s_@@_stop {##3}
\cs_new_eq:NN \@@_generate_internal_test:Nw
\@@_generate_internal_test_aux:w
}
\exp_args:No \@@_tmp:w { \token_to_str:N p }
\cs_new_protected:Npn \@@_generate_internal_one_go:NNn #1#2#3
{
\@@_generate_internal_loop:nwnnw
{ \exp_not:N ##1 } 1 . { } { }
#3 { ? \@@_generate_internal_end:w } X ;
23456789 { ? \@@_generate_internal_long:w } ;
#1 #2 {#3}
}
\cs_new_protected:Npn \@@_generate_internal_loop:nwnnw #1#2 . #3#4#5#6 ; #7
{
\use_none:n #5
\use_none:n #7
\cs_if_exist_use:cF { @@_generate_internal_#5:NN }
{ \@@_generate_internal_other:NN }
#5 #7
#7 .
{ #3 #1 } { #4 ## #2 }
#6 ;
}
\cs_new_protected:Npn \@@_generate_internal_N:NN #1#2
{ \@@_generate_internal_loop:nwnnw { \exp_not:N ###2 } }
\cs_new_protected:Npn \@@_generate_internal_c:NN #1#2
{ \exp_args:No \@@_generate_internal_loop:nwnnw { \exp_not:c {###2} } }
\cs_new_protected:Npn \@@_generate_internal_n:NN #1#2
{ \@@_generate_internal_loop:nwnnw { { \exp_not:n {###2} } } }
\cs_new_protected:Npn \@@_generate_internal_x:NN #1#2
{ \@@_generate_internal_loop:nwnnw { {###2} } }
\cs_new_protected:Npn \@@_generate_internal_other:NN #1#2
{
\exp_args:No \@@_generate_internal_loop:nwnnw
{
\exp_after:wN
{
\exp:w \exp_args:NNc \exp_after:wN \exp_end:
{ exp_not:#1 } {###2}
}
}
}
\cs_new_protected:Npn \@@_generate_internal_end:w #1 . #2#3#4 ; #5 ; #6#7#8
{ #6 { exp_args:N #8 } #3 { #7 {#2} } }
\cs_new_protected:Npn \@@_generate_internal_long:w #1 N #2#3 . #4#5#6#
{
\exp_args:Nx \@@_generate_internal_long:nnnNNn
{ \@@_generate_internal_variant_loop:n #2 #6 { : \use_i:nn } }
{#4} {#5}
}
\cs_new:Npn \@@_generate_internal_long:nnnNNn #1#2#3#4 ; ; #5#6#7
{ #5 { exp_args:N #7 } #3 { #6 { \exp_not:n {#1} {#2} } } }
% \end{macrocode}
% This command grabs char by char outputting |\::#1| (not expanded
% further). We avoid tests by putting a trailing |: \use_i:nn|, which
% leaves \cs{cs_end:} and removes the looping macro. The colon is in
% fact also turned into \cs{:::} so that the required structure for
% |\exp_args:N...| commands is correctly terminated.
% \begin{macrocode}
\cs_new:Npn \@@_generate_internal_variant_loop:n #1
{
\exp_after:wN \exp_not:N \cs:w :: #1 \cs_end:
\@@_generate_internal_variant_loop:n
}
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}
% {
% \prg_generate_conditional_variant:Nnn,
% \@@_generate_variant:nnNnn,
% \@@_generate_variant:w,
% \@@_generate_variant:n,
% \@@_generate_variant_p_form:nnn,
% \@@_generate_variant_T_form:nnn,
% \@@_generate_variant_F_form:nnn,
% \@@_generate_variant_TF_form:nnn,
% }
% \begin{macrocode}
\cs_new_protected:Npn \prg_generate_conditional_variant:Nnn #1
{
\use:e
{
\@@_generate_variant:nnNnn
\cs_split_function:N #1
}
}
\cs_new_protected:Npn \@@_generate_variant:nnNnn #1#2#3#4#5
{
\if_meaning:w \c_false_bool #3
\msg_error:nne { kernel } { missing-colon }
{ \token_to_str:c {#1} }
\@@_use_i_delimit_by_s_stop:nw
\fi:
\exp_after:wN \@@_generate_variant:w
\tl_to_str:n {#5} , \scan_stop: , \q_@@_recursion_stop
\@@_use_none_delimit_by_s_stop:w \s_@@_mark {#1} {#2} {#4} \s_@@_stop
}
\cs_new_protected:Npn \@@_generate_variant:w
#1 , #2 \s_@@_mark #3#4#5
{
\if_meaning:w \scan_stop: #1 \scan_stop:
\if_meaning:w \q_@@_nil #1 \q_@@_nil
\use_i:nnn
\fi:
\exp_after:wN \@@_use_none_delimit_by_q_recursion_stop:w
\else:
\cs_if_exist_use:cTF { @@_generate_variant_#1_form:nnn }
{ {#3} {#4} {#5} }
{
\msg_error:nnee
{ kernel } { conditional-form-unknown }
{#1} { \token_to_str:c { #3 : #4 } }
}
\fi:
\@@_generate_variant:w #2 \s_@@_mark {#3} {#4} {#5}
}
\cs_new_protected:Npn \@@_generate_variant_p_form:nnn #1#2
{ \cs_generate_variant:cn { #1 _p : #2 } }
\cs_new_protected:Npn \@@_generate_variant_T_form:nnn #1#2
{ \cs_generate_variant:cn { #1 : #2 T } }
\cs_new_protected:Npn \@@_generate_variant_F_form:nnn #1#2
{ \cs_generate_variant:cn { #1 : #2 F } }
\cs_new_protected:Npn \@@_generate_variant_TF_form:nnn #1#2
{ \cs_generate_variant:cn { #1 : #2 TF } }
% \end{macrocode}
% \end{macro}
%
% \begin{macro}{\exp_args_generate:n}
% This function is not used in the kernel hence we can use functions
% that are defined in later modules. It also does not need to be fast
% so use inline mappings. For each requested variant we check that
% there are no characters besides |NnpcofVvx|, in particular that
% there are no spaces. Then we just call the internal function.
% \begin{macrocode}
\cs_new_protected:Npn \exp_args_generate:n #1
{
\exp_args:No \clist_map_inline:nn { \tl_to_str:n {#1} }
{
\str_map_inline:nn {##1}
{
\str_if_in:nnF { NnpcofeVvx } {####1}
{
\msg_error:nnnn { kernel } { invalid-exp-args }
{####1} {##1}
\str_map_break:n { \use_none:nn }
}
}
\@@_generate_internal_variant:n {##1}
}
}
% \end{macrocode}
% \end{macro}
%
% \subsection{Definitions with the automated technique}
% \label{sec:l3expan:gendef}
%
% Some of these could be done more efficiently, but the complexity of
% coding then becomes an issue. Notice that the auto-generated functions
% actually take no arguments themselves.
%
% \begin{macro}[EXP]
% {
% \exp_args:Nnc, \exp_args:Nno, \exp_args:NnV, \exp_args:Nnv, \exp_args:Nne, \exp_args:Nnf,
% \exp_args:Noc, \exp_args:Noo, \exp_args:Nof,
% \exp_args:NVo, \exp_args:Nfo, \exp_args:Nff, \exp_args:Nee
% }
% \begin{macro}
% {
% \exp_args:NNx, \exp_args:Ncx, \exp_args:Nnx,
% \exp_args:Nox, \exp_args:Nxo, \exp_args:Nxx,
% }
% Here are the actual function definitions, using the helper
% functions above. The group is used because
% \cs{@@_generate_internal_variant:n} redefines \cs{@@_tmp:w} locally.
% \begin{macrocode}
\cs_set_protected:Npn \@@_tmp:w #1
{
\group_begin:
\exp_args:No \@@_generate_internal_variant:n
{ \tl_to_str:n {#1} }
\group_end:
}
\@@_tmp:w { nc }
\@@_tmp:w { no }
\@@_tmp:w { nV }
\@@_tmp:w { nv }
\@@_tmp:w { ne }
\@@_tmp:w { nf }
\@@_tmp:w { oc }
\@@_tmp:w { oo }
\@@_tmp:w { of }
\@@_tmp:w { Vo }
\@@_tmp:w { fo }
\@@_tmp:w { ff }
\@@_tmp:w { ee }
\@@_tmp:w { Nx }
\@@_tmp:w { cx }
\@@_tmp:w { nx }
\@@_tmp:w { ox }
\@@_tmp:w { xo }
\@@_tmp:w { xx }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}[EXP]
% {
% \exp_args:NNcf,
% \exp_args:NNno, \exp_args:NNnV, \exp_args:NNoo, \exp_args:NNVV,
% \exp_args:Ncno, \exp_args:NcnV, \exp_args:Ncoo, \exp_args:NcVV,
% \exp_args:Nnnc, \exp_args:Nnno, \exp_args:Nnnf, \exp_args:Nnff,
% \exp_args:Nooo, \exp_args:Noof, \exp_args:Nffo, \exp_args:Neee
% }
% \begin{macro}
% {
% \exp_args:NNNx, \exp_args:NNnx, \exp_args:NNox,
% \exp_args:Nccx, \exp_args:Ncnx,
% \exp_args:Nnnx, \exp_args:Nnox, \exp_args:Noox,
% }
% \begin{macrocode}
\@@_tmp:w { Ncf }
\@@_tmp:w { Nno }
\@@_tmp:w { NnV }
\@@_tmp:w { Noo }
\@@_tmp:w { NVV }
\@@_tmp:w { cno }
\@@_tmp:w { cnV }
\@@_tmp:w { coo }
\@@_tmp:w { cVV }
\@@_tmp:w { nnc }
\@@_tmp:w { nno }
\@@_tmp:w { nnf }
\@@_tmp:w { nff }
\@@_tmp:w { ooo }
\@@_tmp:w { oof }
\@@_tmp:w { ffo }
\@@_tmp:w { eee }
\@@_tmp:w { NNx }
\@@_tmp:w { Nnx }
\@@_tmp:w { Nox }
\@@_tmp:w { nnx }
\@@_tmp:w { nox }
\@@_tmp:w { ccx }
\@@_tmp:w { cnx }
\@@_tmp:w { oox }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \subsection{Held-over variant generation}
%
% \begin{macro}[documented-as = \cs_generate_from_arg_count:NNnn]
% {\cs_generate_from_arg_count:NNno}
% \begin{macro}[documented-as = \cs_replacement_spec:N]{\cs_replacement_spec:c}
% A couple of variants that are from early functions.
% \begin{macrocode}
\cs_generate_variant:Nn \cs_generate_from_arg_count:NNnn { NNno }
\cs_generate_variant:Nn \cs_replacement_spec:N { c }
% \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macrocode}
%
% \end{macrocode}
%
% \end{implementation}
%
% \PrintIndex