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-% \iffalse meta-comment
-%
-%% File: l3kernel-functions.dtx
-%
-% Copyright (C) 2018-2024 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}
-%</driver>
-% \fi
-%
-% \title{^^A
-% The \pkg{l3kernel-functions} module\\ Kernel-reserved functions^^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}
-%
-% \end{documentation}
-%
-% \begin{implementation}
-%
-% \section{\pkg{l3kernel-functions}: kernel-reserved functions}
-%
-% \subsection{Internal \pkg{l3debug} kernel functions}
-% \label{sec:l3kernel-functions:l3debug-internals}
-%
-% These function are only created if debugging is enabled, hence they are
-% actually defined in \pkg{l3debug}.
-%
-% \begin{function}{\__kernel_chk_var_local:N, \__kernel_chk_var_global:N}
-% \begin{syntax}
-% \cs{__kernel_chk_var_local:N} \meta{var}
-% \cs{__kernel_chk_var_global:N} \meta{var}
-% \end{syntax}
-% Applies \cs{__kernel_chk_var_exist:N} \meta{var} as well as
-% \cs{__kernel_chk_var_scope:NN} \meta{scope} \meta{var}, where
-% \meta{scope} is |l| or~|g|.
-% \end{function}
-%
-% \begin{function}{\__kernel_chk_var_scope:NN}
-% \begin{syntax}
-% \cs{__kernel_chk_var_scope:NN} \meta{scope} \meta{var}
-% \end{syntax}
-% Checks the \meta{var} has the correct \meta{scope}, and if not
-% raises a kernel-level error.
-% The \meta{scope} is a single letter |l|, |g|,
-% |c| denoting local variables, global variables, or constants. More
-% precisely, if the variable name starts with a letter and an
-% underscore (normal \pkg{expl3} convention) the function checks that
-% this single letter matches the \meta{scope}. Otherwise the function
-% cannot know the scope \meta{var} the first time: instead, it defines
-% |\__debug_chk_/|\meta{var name} to store that information for the
-% next call. Thus, if a given \meta{var} is subject to assignments of
-% different scopes a kernel error will result.
-% \end{function}
-%
-% \begin{function}
-% {
-% \__kernel_chk_cs_exist:N,
-% \__kernel_chk_cs_exist:c,
-% \__kernel_chk_var_exist:N
-% }
-% \begin{syntax}
-% \cs{__kernel_chk_cs_exist:N} \meta{cs}
-% \cs{__kernel_chk_var_exist:N} \meta{var}
-% \end{syntax}
-% Checks that their argument is defined according to the criteria for
-% \cs{cs_if_exist_p:N},
-% and if not raises a kernel-level error. Error messages are
-% different.
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_chk_flag_exist:NN}
-% \begin{syntax}
-% \cs{__kernel_chk_flag_exist:NN}
-% \meta{function} \meta{flag}
-% \end{syntax}
-% Checks that the \meta{flag} is defined according to the criterion for
-% \cs{flag_if_exist_p:N}, and if not raises a kernel-level error and
-% calls the function with the argument \cs{l_tmpa_flag} to proceed
-% somehow without producing too many errors.
-% \end{function}
-%
-% \begin{function}{\__kernel_debug_log:e}
-% \begin{syntax}
-% \cs{__kernel_debug_log:e} \Arg{message text}
-% \end{syntax}
-% If the \texttt{log-functions} option is active, this function writes
-% the \meta{message text} to the log file using \cs{iow_log:e}.
-% Otherwise, the \meta{message text} is ignored using \cs{use_none:n}.
-% \end{function}
-%
-% \subsection{Internal kernel functions}
-%
-% \begin{function}{\__kernel_chk_defined:NT}
-% \begin{syntax}
-% \cs{__kernel_chk_defined:NT} \meta{variable} \Arg{true code}
-% \end{syntax}
-% If \meta{variable} is not defined (according to
-% \cs{cs_if_exist:NTF}), this triggers an error, otherwise the
-% \meta{true code} is run.
-% \end{function}
-%
-% \begin{function}{\__kernel_chk_expr:nNnN}
-% \begin{syntax}
-% \cs{__kernel_chk_expr:nNnN} \Arg{expr} \meta{eval} \Arg{convert} \meta{caller}
-% \end{syntax}
-% This function is only created if debugging is enabled. By default
-% it is equivalent to \cs{use_i:nnnn}. When expression checking is
-% enabled, it leaves in the input stream the result of \cs{tex_the:D}
-% \meta{eval} \meta{expr} \cs{tex_relax:D} after checking that no
-% token was left over. If any token was not taken as part of the
-% expression, there is an error message displaying the result of the
-% evaluation as well as the \meta{caller}. For instance \meta{eval}
-% can be \cs{__int_eval:w} and \meta{caller} can be \cs{int_eval:n} or
-% \cs{int_set:Nn}. The argument \meta{convert} is empty except for mu
-% expressions where it is \cs{tex_mutoglue:D}, used for internal
-% purposes.
-% \end{function}
-%
-% \begin{function}{\__kernel_chk_tl_type:NnnT}
-% \begin{syntax}\parskip=0pt\obeylines
-% \cs{__kernel_chk_tl_type:NnnT} \meta{control sequence} \Arg{specific type} \\
-% | |\Arg{reconstruction} \Arg{true code}
-% \end{syntax}
-% Helper to test that the \meta{control sequence} is a variable of the
-% given \meta{specific type} of token list. Produces suitable error
-% messages if the \meta{control sequence} does not exist, or if it is
-% not a token list variable at all, or if the \meta{control sequence}
-% differs from the result of |e|-expanding \meta{reconstruction}. If
-% all of these tests succeed then the \meta{true code} is run.
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_codepoint_to_bytes:n}
-% \begin{syntax}
-% \cs{__kernel_codepoint_to_bytes:n} \Arg{codepoint}
-% \end{syntax}
-% Converts the \meta{codepoint} to UTF-8 bytes. The expansion
-% of this function comprises four brace groups, each of which will contain
-% a hexadecimal value: the appropriate byte. As UTF-8 is a variable-length,
-% one or more of the groups may be empty: the bytes read in the logical order,
-% such that a two-byte codepoint will have groups |#1| and |#2| filled
-% and |#3| and |#4| empty.
-% \end{function}
-%
-% \begin{function}{\__kernel_cs_parm_from_arg_count:nnF}
-% \begin{syntax}
-% \cs{__kernel_cs_parm_from_arg_count:nnF} \Arg{follow-on} \Arg{args} \Arg{false code}
-% \end{syntax}
-% Evaluates the number of \meta{args} and leaves the \meta{follow-on} code
-% followed by a brace group containing the required number of primitive
-% parameter markers (|#1|, \emph{etc}.). If the number of \meta{args} is outside
-% the range $[0,9]$, the \meta{false code} is inserted \emph{instead} of
-% the \meta{follow-on}.
-% \end{function}
-%
-% \begin{function}{
-% \__kernel_dependency_version_check:Nn,
-% \__kernel_dependency_version_check:nn,
-% }
-% \begin{syntax}
-% \cs{__kernel_dependency_version_check:Nn} \Arg{\cs{date}} \Arg{file}
-% \cs{__kernel_dependency_version_check:nn} \Arg{date} \Arg{file}
-% \end{syntax}
-% Checks if the loaded version of the \pkg{expl3} kernel is at least \meta{date},
-% required by \meta{file}. If the kernel date is older than \meta{date}, the
-% loading of \meta{file} is aborted and an error is raised.
-% \end{function}
-%
-% \begin{function}{\__kernel_deprecation_code:nn}
-% \begin{syntax}
-% \cs{__kernel_deprecation_code:nn} \Arg{error code} \Arg{working code}
-% \end{syntax}
-% Stores both an \meta{error} and \meta{working} definition for given material
-% such that they can be exchanged by \cs{debug_on:n} and \cs{debug_off:n}.
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_exp_not:w}
-% \begin{syntax}
-% \cs{__kernel_exp_not:w} \meta{expandable tokens} \Arg{content}
-% \end{syntax}
-% Carries out expansion on the \meta{expandable tokens} before preventing
-% further expansion of the \meta{content} as for \cs{exp_not:n}. Typically,
-% the \meta{expandable tokens} will alter the nature of the \meta{content},
-% \emph{i.e.}~allow it to be generated in some way.
-% \end{function}
-%
-% \begin{variable}{\l__kernel_expl_bool}
-% A boolean which records the current code syntax status: \texttt{true} if
-% currently inside a code environment. This variable should only be
-% set by \cs{ExplSyntaxOn}/\cs{ExplSyntaxOff}.
-% \end{variable}
-%
-% \begin{variable}{\c__kernel_expl_date_tl}
-% A token list containing the release date of the \pkg{l3kernel} preloaded
-% in \LaTeXe{} used to check if dependencies match.
-% \end{variable}
-%
-% \begin{function}{\__kernel_file_missing:n}
-% \begin{syntax}
-% \cs{__kernel_file_missing:n} \Arg{name}
-% \end{syntax}
-% Expands the \meta{name} as per \cs{__kernel_file_name_sanitize:n} then
-% produces an error message indicating that this file was not found.
-% \end{function}
-%
-% \begin{function}[EXP,updated = 2021-04-17]{\__kernel_file_name_sanitize:n}
-% \begin{syntax}
-% \cs{__kernel_file_name_sanitize:n} \Arg{name}
-% \end{syntax}
-% Expands the file name using a \tn{csname}-based approach, and
-% relies on active characters (for example from UTF-8 characters)
-% being properly set up to expand to a expansion-safe version using
-% \cs{ifcsname}. This is less conservative than the token-by-token
-% approach used before, but it is much faster.
-% \end{function}
-%
-% \begin{function}{\__kernel_file_input_push:n, \__kernel_file_input_pop:}
-% \begin{syntax}
-% \cs{__kernel_file_input_push:n} \Arg{name}
-% \cs{__kernel_file_input_pop:}
-% \end{syntax}
-% Used to push and pop data from the internal file stack: needed only
-% in package mode, where interfacing with the \LaTeXe{} kernel is necessary.
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_int_add:nnn}
-% \begin{syntax}
-% \cs{__kernel_int_add:nnn} \Arg{integer_1} \Arg{integer_2} \Arg{integer_3}
-% \end{syntax}
-% Expands to the result of adding the three \meta{integers} (which
-% must be suitable input for \cs{int_eval:w}), avoiding intermediate
-% overflow. Overflow occurs only if the overall result is outside
-% $[-2^{31}+1,2^{31}-1]$. The \meta{integers} may be of the form
-% \cs{int_eval:w} \dots{} \cs{scan_stop:} but may be evaluated more
-% than once.
-% \end{function}
-%
-% \begin{function}[added = 2018-03-31]{\__kernel_intarray_gset:Nnn}
-% \begin{syntax}
-% \cs{__kernel_intarray_gset:Nnn} \meta{intarray~var} \Arg{index} \Arg{value}
-% \end{syntax}
-% Faster version of \cs{intarray_gset:Nnn}. Stores the \meta{value}
-% into the \meta{integer array variable} at the \meta{position}. The
-% \meta{index} and \meta{value} must be suitable for a direct
-% assignment to a \TeX{} count register, for instance expanding to an
-% integer denotation or obtained through the primitive \tn{numexpr}
-% (which may be un-terminated). No bound checking is performed: the
-% caller is responsible for ensuring that the \meta{position} is
-% between $1$ and the \cs{intarray_count:N}, and the \meta{value}'s
-% absolute value is at most $2^{30}-1$. Assignments are always
-% global.
-% \end{function}
-%
-% \begin{function}[EXP, added = 2018-03-31]{\__kernel_intarray_item:Nn}
-% \begin{syntax}
-% \cs{__kernel_intarray_item:Nn} \meta{intarray~var} \Arg{index}
-% \end{syntax}
-% Faster version of \cs{intarray_item:Nn}. Expands to the integer
-% entry stored at the \meta{index} in the \meta{integer array
-% variable}. The \meta{index} must be suitable for a direct
-% assignment to a \TeX{} count register and must be between $1$ and
-% the \cs{intarray_count:N}, lest a low-level \TeX{} error occur.
-% \end{function}
-%
-% \begin{function}[rEXP, added = 2020-07-12]{\__kernel_intarray_range_to_clist:Nnn}
-% \begin{syntax}
-% \cs{__kernel_intarray_range_to_clist:Nnn} \meta{intarray~var} \Arg{start index} \Arg{end index}
-% \end{syntax}
-% Converts to integer denotations separated by commas the entries of
-% the \meta{intarray} from positions \meta{start index} to \meta{end
-% index} included. The \meta{start index} and \meta{end index} must
-% be suitable for a direct assignment to a \TeX{} count register, must
-% be between $1$ and the \cs{intarray_count:N}, and be suitably
-% ordered. All tokens have category code other.
-% \end{function}
-%
-% \begin{function}[added = 2020-07-12]{\__kernel_intarray_gset_range_from_clist:Nnn}
-% \begin{syntax}
-% \cs{__kernel_intarray_gset_range_from_clist:Nnn} \meta{intarray~var} \Arg{start index} \Arg{integer clist}
-% \end{syntax}
-% Stores the entries of the \meta{clist} as entries of the
-% \meta{intarray~var} starting from the \meta{start index}, upwards.
-% This is done without any bound checking. The \meta{start index} and
-% all entries of the \meta{integer comma list} (which do not undergo
-% space trimming and brace stripping as in normal clist mappings) must
-% be suitable for a direct assignment to a \TeX{} count register. An
-% empty entry may stop the loop.
-% \end{function}
-%
-% \begin{function}{\__kernel_ior_open:Nn, \__kernel_ior_open:No}
-% \begin{syntax}
-% \cs{__kernel_ior_open:Nn} \meta{stream} \Arg{file name}
-% \end{syntax}
-% This function has identical syntax to the public version. However,
-% is does not take precautions against active characters in the
-% \meta{file name}, and it does not attempt to add a \meta{path} to
-% the \meta{file name}: it is therefore intended to be used by
-% higher-level
-% functions which have already fully expanded the \meta{file name} and which
-% need to perform multiple open or close operations. See for example the
-% implementation of \cs{file_get_full_name:nN},
-% \end{function}
-%
-% \begin{function}{\__kernel_iow_with:Nnn}
-% \begin{syntax}
-% \cs{__kernel_iow_with:Nnn} \meta{integer} \Arg{value} \Arg{code}
-% \end{syntax}
-% If the \meta{integer} is equal to the \meta{value} then this
-% function simply runs the \meta{code}. Otherwise it saves the
-% current value of the \meta{integer}, sets it to the \meta{value},
-% runs the \meta{code}, and restores the \meta{integer} to its former
-% value. This is used to ensure that the \tn{newlinechar} is~$10$
-% when writing to a stream, which lets \cs{iow_newline:} work, and
-% that \tn{errorcontextlines} is $-1$ when displaying a message.
-% \end{function}
-%
-% \begin{variable}{\__kernel_kern:n}
-% \begin{syntax}
-% \cs{__kernel_kern:n} \Arg{length}
-% \end{syntax}
-% Inserts a kern of the specified \meta{length}, a dimension expression.
-% \end{variable}
-%
-% \begin{function}{\__kernel_msg_show_eval:Nn, \__kernel_msg_log_eval:Nn}
-% \begin{syntax}
-% \cs{__kernel_msg_show_eval:Nn} \meta{function} \Arg{expression}
-% \end{syntax}
-% Shows or logs the \meta{expression} (turned into a string), an equal
-% sign, and the result of applying the \meta{function} to the
-% \Arg{expression} (with \texttt{f}-expansion). For instance, if the
-% \meta{function} is \cs{int_eval:n} and the \meta{expression} is
-% |1+2| then this logs |> 1+2=3.|
-% \end{function}
-%
-% \begin{variable}{\g__kernel_prg_map_int}
-% This integer is used by non-expandable mapping functions to track
-% the level of nesting in force. The functions
-% \cs[no-index]{\meta{type}_map_1:w},
-% \cs[no-index]{\meta{type}_map_2:w}, \emph{etc.}, labelled by
-% \cs{g__kernel_prg_map_int}
-% hold functions to be mapped over various list datatypes in inline
-% and variable mappings.
-% \end{variable}
-%
-% \begin{function}{\__kernel_quark_new_test:N}
-% \begin{syntax}
-% \cs{__kernel_quark_new_test:N} \cs[no-index]{\meta{name}:\meta{arg spec}}
-% \end{syntax}
-% Defines a quark-test function \cs[no-index]{\meta{name}:\meta{arg spec}}
-% which tests if its argument is \cs[no-index]{q__\meta{namespace}_recursion_tail},
-% then acts accordingly, as described below for each possible
-% \meta{arg spec}.
-%
-% The \meta{namespace} is determined as the first (nonempty)
-% |_|-delimited word in \meta{name} and is used internally
-% in the definition of auxiliaries. The function
-% \cs{__kernel_quark_new_test:N} does \emph{not} define
-% the \cs[no-index]{q__\meta{namespace}_recursion_tail} and
-% \cs[no-index]{q__\meta{namespace}_recursion_stop} quarks.
-% They should be manually defined with \cs{quark_new:N}.
-%
-% There are $6$ different types of quark-test functions. Which one is
-% defined depends on the \meta{arg spec}, which \emph{must} be one of
-% the options listed now. Four of them are modeled after
-% \cs[no-index]{quark_if_recursion_tail:(N|n)} and
-% \cs[no-index]{quark_if_recursion_tail_do:(N|n)n}.
-% \begin{description}
-% \def\makelabel#1{\texttt{#1}}
-% \item[n] defines \cs[no-index]{\meta{name}:n} such that it
-% checks if |#1| contains only \cs[no-index]{q__\meta{namespace}_recursion_tail}, and
-% if so consumes all tokens up to \cs[no-index]{q__\meta{namespace}_recursion_stop}
-% (\emph{c.f.}~\cs{quark_if_recursion_tail_stop:n}).
-% \item[nn] defines \cs[no-index]{\meta{name}:nn} such that it
-% checks if |#1| contains only \cs[no-index]{q__\meta{namespace}_recursion_tail}, and
-% if so consumes all tokens up to \cs[no-index]{q__\meta{namespace}_recursion_stop},
-% then executes the code |#2| after that
-% (\emph{c.f.}~\cs{quark_if_recursion_tail_stop_do:nn}).
-% \item[N] defines \cs[no-index]{\meta{name}:N} such that it
-% checks if |#1| is \cs[no-index]{q__\meta{namespace}_recursion_tail}, and if so consumes
-% all tokens up to \cs[no-index]{q__\meta{namespace}_recursion_stop}
-% (\emph{c.f.}~\cs{quark_if_recursion_tail_stop:N}).
-% \item[Nn] defines \cs[no-index]{\meta{name}:Nn} such that it
-% checks if |#1| is \cs[no-index]{q__\meta{namespace}_recursion_tail}, and if so consumes
-% all tokens up to \cs[no-index]{q__\meta{namespace}_recursion_stop}, then executes
-% the code |#2| after that
-% (\emph{c.f.}~\cs{quark_if_recursion_tail_stop_do:Nn}).
-% \end{description}
-% The last two are modeled after
-% \cs[no-index]{quark_if_recursion_tail_break:(n|N)N}, and in those
-% cases the quark \cs[no-index]{q__\meta{namespace}_recursion_stop} is
-% not used (and thus needs not be defined).
-% \begin{description}
-% \def\makelabel#1{\texttt{#1}}
-% \item[nN] defines \cs[no-index]{\meta{name}:nN} such that it
-% checks if |#1| contains only \cs[no-index]{q__\meta{namespace}_recursion_tail}, and
-% if so uses the \cs[no-index]{\meta{type}_map_break:} function |#2|.
-% \item[NN] defines \cs[no-index]{\meta{name}:NN} such that it
-% checks if |#1| is \cs[no-index]{q__\meta{namespace}_recursion_tail}, and if so uses
-% the \cs[no-index]{\meta{type}_map_break:} function |#2|.
-% \end{description}
-% Any other signature, as well as a function without signature
-% are errors, and in such case the definition is aborted.
-% \end{function}
-%
-% \begin{function}{\__kernel_quark_new_conditional:Nn}
-% \begin{syntax}
-% \cs{__kernel_quark_new_conditional:Nn} \cs[no-index]{__\meta{namespace}_quark_if_\meta{name}:\meta{arg spec}} \Arg{conditions}
-% \end{syntax}
-% Defines a collection of quark conditionals that test if their
-% argument is the quark \cs[no-index]{q__\meta{namespace}_\meta{name}}
-% and perform suitable actions. The \meta{conditions} are a
-% comma-separated list of one or more of |p|, |T|, |F|, and |TF|, and
-% one conditional is defined for each \meta{condition} in the list, as
-% described for \cs{prg_new_conditional:Npnn}. The conditionals are
-% defined using \cs{prg_new_conditional:Npnn}, so that their name is
-% obtained by adding |p|, |T|, |F|, or |TF| to the base name
-% \cs[no-index]{__\meta{namespace}_quark_if_\meta{name}:\meta{arg spec}}.
-%
-% The first argument of \cs{__kernel_quark_new_conditional:Nn} must
-% contain |_quark_if_| and |:|, as these markers are used to determine
-% the \meta{name} of the quark
-% \cs[no-index]{q__\meta{namespace}_\meta{name}} to be tested. This
-% quark should be manually defined with \cs{quark_new:N}, as
-% \cs{__kernel_quark_new_conditional:Nn} does \emph{not} define it.
-%
-% The function \cs{__kernel_quark_new_conditional:Nn} can define $2$
-% different types of quark conditionals. Which one is defined depends
-% on the \meta{arg spec}, which \emph{must} be one of the following
-% options, modeled after \cs[index=quark_if_nil:NTF]{quark_if_nil:(N|n)(TF)}.
-% \begin{description}
-% \def\makelabel#1{\texttt{#1}}
-% \item[n] defines \cs[no-index]{__\meta{namespace}_quark_if_\meta{name}:n(TF)} such that it
-% checks if |#1| contains only \cs[no-index]{q__\meta{namespace}_\meta{name}}, and
-% executes the proper conditional branch.
-% \item[N] defines \cs[no-index]{__\meta{namespace}_quark_if_\meta{name}:N(TF)} such that it
-% checks if |#1| is \cs[no-index]{q__\meta{namespace}_\meta{name}}, and
-% executes the proper conditional branch.
-% \end{description}
-% Any other signature, as well as a function without signature
-% are errors, and in such case the definition is aborted.
-% \end{function}
-%
-% \begin{function}{\__kernel_sys_everyjob:}
-% \begin{syntax}
-% \cs{__kernel_sys_everyjob:}
-% \end{syntax}
-% Inserts the internal token list required at the start of every run (job).
-% \end{function}
-%
-% \begin{variable}{\c__kernel_randint_max_int}
-% Maximal allowed argument to \cs{__kernel_randint:n}. Equal to
-% $2^{17}-1$.
-% \end{variable}
-%
-% \begin{function}{\__kernel_randint:n}
-% \begin{syntax}
-% \cs{__kernel_randint:n} \Arg{max}
-% \end{syntax}
-% Used in an integer expression this gives a pseudo-random number
-% between $1$ and $\meta{max}$ included. One must have
-% $\meta{max}\leq 2^{17}-1$. The \meta{max} must be suitable for
-% \cs{int_value:w} (and any \cs{int_eval:w} must be terminated by
-% \cs{scan_stop:} or equivalent).
-% \end{function}
-%
-% \begin{function}{\__kernel_randint:nn}
-% \begin{syntax}
-% \cs{__kernel_randint:nn} \Arg{min} \Arg{max}
-% \end{syntax}
-% Used in an integer expression this gives a pseudo-random number
-% between $\meta{min}$ and $\meta{max}$ included. The \meta{min} and
-% \meta{max} must be suitable for \cs{int_value:w} (and any
-% \cs{int_eval:w} must be terminated by \cs{scan_stop:} or
-% equivalent). For small ranges
-% $R=\meta{max}-\meta{min}+1\leq 2^{17}-1$,
-% $\meta{min} - 1 + \cs{__kernel_randint:n} |{|R|}|$ is faster.
-% \end{function}
-%
-% \begin{function}{\__kernel_register_show:N, \__kernel_register_show:c}
-% \begin{syntax}
-% \cs{__kernel_register_show:N} \meta{register}
-% \end{syntax}
-% Used to show the contents of a \TeX{} register at the terminal, formatted
-% such that internal parts of the mechanism are not visible.
-% \end{function}
-%
-% \begin{function}
-% {\__kernel_register_log:N, \__kernel_register_log:c}
-% \begin{syntax}
-% \cs{__kernel_register_log:N} \meta{register}
-% \end{syntax}
-% Used to write the contents of a \TeX{} register to the log file in a
-% form similar to \cs{__kernel_register_show:N}.
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_str_to_other:n}
-% \begin{syntax}
-% \cs{__kernel_str_to_other:n} \Arg{token list}
-% \end{syntax}
-% Converts the \meta{token list} to a \meta{other string}, where
-% spaces have category code \enquote{other}. This function can be
-% \texttt{f}-expanded without fear of losing a leading space, since
-% spaces do not have category code $10$ in its result. It takes a
-% time quadratic in the character count of the string.
-% \end{function}
-%
-% \begin{function}[rEXP]{\__kernel_str_to_other_fast:n}
-% \begin{syntax}
-% \cs{__kernel_str_to_other_fast:n} \Arg{token list}
-% \end{syntax}
-% Same behaviour \cs{__kernel_str_to_other:n} but only restricted-expandable.
-% It takes a time linear in the character count of the string.
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_tl_to_str:w}
-% \begin{syntax}
-% \cs{__kernel_tl_to_str:w} \meta{expandable tokens} \Arg{tokens}
-% \end{syntax}
-% Carries out expansion on the \meta{expandable tokens} before conversion of
-% the \meta{tokens} to a string as describe for \cs{tl_to_str:n}. Typically,
-% the \meta{expandable tokens} will alter the nature of the \meta{tokens},
-% \emph{i.e.}~allow it to be generated in some way. This function requires
-% only a single expansion.
-% \end{function}
-%
-% \begin{function}{\__kernel_tl_set:Nx, \__kernel_tl_gset:Nx}
-% \begin{syntax}
-% \cs{__kernel_tl_set:Nx} \meta{tl~var} \Arg{tokens}
-% \end{syntax}
-% Fully expands \meta{tokens} and assigns the result to \meta{tl~var}.
-% \meta{tokens} must be given in braces and there must be no token between
-% \meta{tl~var} and \meta{tokens}.
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_codepoint_data:nn}
-% \begin{syntax}
-% \cs{__kernel_codepoint_data:nn} \Arg{type} \Arg{codepoint}
-% \end{syntax}
-% Expands to the appropriate value for the \meta{type} of data
-% requested for a \meta{codepoint}. The current list of \meta{types} and
-% results are
-% \begin{description}
-% \item[\texttt{lowercase}] The \emph{single} codepoint specified by
-% \texttt{UnicodeData.txt} for lowercase mapping of the codepoint:
-% will be equal to the input \meta{codepoint} if there is no mapping
-% specified in \texttt{UnicodeData.txt}
-% \item[\texttt{uppercase}] The \emph{single} codepoint specified by
-% \texttt{UnicodeData.txt} for uppercase mapping of the codepoint:
-% will be equal to the input \meta{codepoint} if there is no mapping
-% specified in \texttt{UnicodeData.txt}
-% \end{description}
-% \end{function}
-%
-% \begin{function}[EXP]{\__kernel_codepoint_case:nn}
-% \begin{syntax}
-% \cs{__kernel_codepoint_case:nn} \Arg{mapping} \Arg{codepoint}
-% \end{syntax}
-% Expands to a list of three balanced text, of which at least the first
-% will contain a codepoint. This list of up to three codepoints specifies
-% the full case mapping for the input \meta{codepoint}. The \meta{mapping}
-% should be one of
-% \begin{itemize}
-% \item \texttt{casefold}
-% \item \texttt{lowercase}
-% \item \texttt{titlecase}
-% \item \texttt{uppercase}
-% \end{itemize}
-% \end{function}
-%
-% \subsection{Kernel backend functions}
-%
-% These functions are required to pass information to the backend. The nature
-% of these means that they are defined only when the relevant backend is in
-% use.
-%
-% \begin{function}
-% {
-% \__kernel_backend_literal:n,
-% \__kernel_backend_literal:e,
-% \__kernel_backend_literal:e
-% }
-% \begin{syntax}
-% \cs{__kernel_backend_literal:n} \Arg{content}
-% \end{syntax}
-% Adds the \meta{content} literally to the current vertical list as a
-% whatsit. The nature of the \meta{content} will depend on the backend in
-% use.
-% \end{function}
-%
-% \begin{function}
-% {
-% \__kernel_backend_literal_postscript:n,
-% \__kernel_backend_literal_postscript:e
-% }
-% \begin{syntax}
-% \cs{__kernel_backend_literal_postscript:n} \Arg{PostScript}
-% \end{syntax}
-% Adds the \meta{PostScript} literally to the current vertical list as a
-% whatsit. No positioning is applied.
-% \end{function}
-%
-% \begin{function}
-% {
-% \__kernel_backend_literal_pdf:n,
-% \__kernel_backend_literal_pdf:e
-% }
-% \begin{syntax}
-% \cs{__kernel_backend_literal_pdf:n} \Arg{PDF instructions}
-% \end{syntax}
-% Adds the \meta{PDF instructions} literally to the current vertical list as
-% a whatsit. No positioning is applied.
-% \end{function}
-%
-% \begin{function}
-% {
-% \__kernel_backend_literal_svg:n,
-% \__kernel_backend_literal_svg:e
-% }
-% \begin{syntax}
-% \cs{__kernel_backend_literal_svg:n} \Arg{SVG instructions}
-% \end{syntax}
-% Adds the \meta{SVG instructions} literally to the current vertical list as
-% a whatsit. No positioning is applied.
-% \end{function}
-%
-% \begin{function}
-% {
-% \__kernel_backend_postscript:n,
-% \__kernel_backend_postscript:e
-% }
-% \begin{syntax}
-% \cs{__kernel_backend_postscript:n} \Arg{PostScript}
-% \end{syntax}
-% Adds the \meta{PostScript} to the current vertical list as a
-% whatsit. The PostScript reference point is adjusted to match the
-% current position. The PostScript is inserted inside a |SDict begin|/|end|
-% pair.
-% \end{function}
-%
-% \begin{function}{\__kernel_backend_align_begin:, \__kernel_backend_align_end:}
-% \begin{syntax}
-% \cs{__kernel_backend_align_begin:}
-% \meta{PostScript literals}
-% \cs{__kernel_backend_align_end:}
-% \end{syntax}
-% Arranges to align the PostScript and DVI current positions and scales.
-% \end{function}
-%
-% \begin{function}{\__kernel_backend_scope_begin:, \__kernel_backend_scope_end:}
-% \begin{syntax}
-% \cs{__kernel_backend_scope_begin:}
-% \meta{content}
-% \cs{__kernel_backend_scope_end:}
-% \end{syntax}
-% Creates a scope for instructions at the backend level.
-% \end{function}
-%
-% \begin{function}
-% {
-% \__kernel_backend_matrix:n,
-% \__kernel_backend_matrix:e
-% }
-% \begin{syntax}
-% \cs{__kernel_backend_matrix:n} \Arg{matrix}
-% \end{syntax}
-% Applies the \meta{matrix} to the current transformation matrix.
-% \end{function}
-%
-% \begin{function}{\g__kernel_backend_header_bool}
-% Specifies whether to write headers for the backend.
-% \end{function}
-%
-% \begin{function}{\l__kernel_color_stack_int}
-% The color stack used in \pdfTeX{} and \LuaTeX{} for the main color.
-% \end{function}
-%
-% \end{implementation}
-%
-% \PrintIndex