From 0bc9393ae50667d7ff769a76321a9548a70351fc Mon Sep 17 00:00:00 2001
From: Karl Berry <karl@freefriends.org>
Date: Thu, 29 Dec 2011 23:03:28 +0000
Subject: l3experimental 3109 (29dec11)

git-svn-id: svn://tug.org/texlive/trunk@24970 c570f23f-e606-0410-a88d-b1316a301751
---
 .../source/latex/l3experimental/l3str/l3flag.dtx   | 236 +++++++++++++++++++++
 1 file changed, 236 insertions(+)
 create mode 100644 Master/texmf-dist/source/latex/l3experimental/l3str/l3flag.dtx

(limited to 'Master/texmf-dist/source/latex/l3experimental/l3str/l3flag.dtx')

diff --git a/Master/texmf-dist/source/latex/l3experimental/l3str/l3flag.dtx b/Master/texmf-dist/source/latex/l3experimental/l3str/l3flag.dtx
new file mode 100644
index 00000000000..eed657ad231
--- /dev/null
+++ b/Master/texmf-dist/source/latex/l3experimental/l3str/l3flag.dtx
@@ -0,0 +1,236 @@
+% \iffalse meta-comment
+%
+%% File: l3flag.dtx Copyright (C) 2011 The LaTeX3 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
+%%
+%%    http://www.latex-project.org/lppl.txt
+%%
+%% This file is part of the "l3experimental bundle" (The Work in LPPL)
+%% and all files in that bundle must be distributed together.
+%%
+%% The released version of this bundle is available from CTAN.
+%%
+%% -----------------------------------------------------------------------
+%%
+%% The development version of the bundle can be found at
+%%
+%%    http://www.latex-project.org/svnroot/experimental/trunk/
+%%
+%% for those people who are interested.
+%%
+%%%%%%%%%%%
+%% NOTE: %%
+%%%%%%%%%%%
+%%
+%%   Snapshots taken from the repository represent work in progress and may
+%%   not work or may contain conflicting material!  We therefore ask
+%%   people _not_ to put them into distributions, archives, etc. without
+%%   prior consultation with the LaTeX3 Project.
+%%
+%% -----------------------------------------------------------------------
+%
+%<*driver|package>
+\RequirePackage{expl3}
+\GetIdInfo$Id: l3flag.dtx 3039 2011-12-08 09:22:35Z bruno $
+  {L3 Experimental Flags}
+%</driver|package>
+%<*driver>
+\documentclass[full]{l3doc}
+\usepackage{amsmath}
+\begin{document}
+  \DocInput{\jobname.dtx}
+\end{document}
+%</driver>
+% \fi
+%
+%
+% \title{^^A
+%   The \textsf{l3flag} package: expandable flags^^A
+%   \thanks{This file describes v\ExplFileVersion,
+%     last revised \ExplFileDate.}^^A
+% }
+%
+% \author{^^A
+%  The \LaTeX3 Project\thanks
+%    {^^A
+%      E-mail:
+%        \href{mailto:latex-team@latex-project.org}
+%          {latex-team@latex-project.org}^^A
+%    }^^A
+% }
+%
+% \date{Released \ExplFileDate}
+%
+% \maketitle
+%
+% \begin{documentation}
+%
+% Flags are the only data structure on which \TeX{} can perform
+% assignments in expansion only contexts. This module is meant
+% mostly for kernel use: in almost all cases, booleans should
+% be preferred to flags, because they are faster.
+%
+% A flag can be in two states: \enquote{lowered} or \enquote{raised}.
+% The status of a flag can be tested expandably (just like booleans).
+% A flag can also be \emph{raised} expandably. However, a flag cannot
+% be lowered expandably.
+%
+% Flag variables are always local.
+%
+% Testing for the existence of flags with \cs{cs_if_exist:NTF} will
+% always result in a negative answer: from the point of view of
+% \TeX{}, flags are either undefined control sequences, or let to
+% \cs{scan_stop:}. This has a second consequence: flags don't need
+% to be declared with \cs{flag_new:N}, although this has error-checking
+% benefits. The ability of using flags without declaring them is used
+% in \pkg{l3rand}.
+%
+% \begin{function}{\flag_new:N, \flag_new:c}
+%   \begin{syntax}
+%     \cs{flag_new:N} \meta{flag}
+%   \end{syntax}
+%   Creates a new \meta{flag} or raises an error if the
+%   name is already taken. The declaration is global,
+%   but \meta{flags} are always local variables.
+%   The \meta{flag} will initially be lowered.
+% \end{function}
+%
+% \begin{function}[EXP,pTF]{\flag_test:N, \flag_test:c}
+%   \begin{syntax}
+%     \cs{flag_test:N} \meta{flag}
+%   \end{syntax}
+%   This function returns \texttt{true} if the \meta{flag} is raised,
+%   and \texttt{false} if the \meta{flag} is lowered.
+% \end{function}
+%
+% \begin{function}[EXP]{\flag_raise:N}
+%   \begin{syntax}
+%     \cs{flag_raise:N} \meta{flag}
+%   \end{syntax}
+%   The \meta{flag} is raised. The assignment is local.
+%   This function is expandable, despite being an assignment.
+% \end{function}
+%
+% \begin{function}{\flag_lower:N}
+%   \begin{syntax}
+%     \cs{flag_lower:N} \meta{flag}
+%   \end{syntax}
+%   The \meta{flag} is lowered. The assignment is local.
+% \end{function}
+%
+% \end{documentation}
+%
+% \begin{implementation}
+%
+% \section{\pkg{l3str} implementation}
+%
+%    \begin{macrocode}
+%<*initex|package>
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+\ProvidesExplPackage
+  {\ExplFileName}{\ExplFileDate}{\ExplFileVersion}{\ExplFileDescription}
+%    \end{macrocode}
+%
+% \begin{variable}{\g_flag_list_tl}
+%   We keep track of the list of all defined flags in a token list.
+%   This is only used by \cs{flag_new:N} to check that the flag
+%   has not yet been defined.
+%    \begin{macrocode}
+\tl_new:N \g_flag_list_tl
+%    \end{macrocode}
+% \end{variable}
+%
+% \begin{macro}{\flag_new:N, \flag_new:c}
+%   If the control sequence is already defined, then we raise an error.
+%   Otherwise we check if it is already a flag, raising an appropriate
+%   error, finally lower the flag globally (this is the only global
+%   assignment to a flag\ldots{} perhaps an error?).
+%   The \texttt{c} variant can be created without worrying for this function.
+%   \begin{macrocode}
+\cs_new_protected:Npn \flag_new:N #1
+  {
+    \tl_if_in:NnTF \g_flag_list_tl {#1}
+      {
+        \msg_kernel_error:nnx
+          { flag } { already-defined }
+          { \token_to_str:N #1 }
+      }
+      {
+        \tl_gput_right:Nn \g_flag_list_tl {#1}
+        \cs_new_eq:NN #1 \c_undefined:D
+      }
+  }
+\cs_generate_variant:Nn \flag_new:N { c }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP, pTF]{\flag_test:N, \flag_test:c}
+%   Test if the control sequence is \texttt{undefined} or not.
+%    \begin{macrocode}
+\prg_new_conditional:Npnn \flag_test:N #1 { p , T , F , TF }
+  {
+    \if_cs_exist:N #1
+      \prg_return_true:
+    \else:
+      \prg_return_false:
+    \fi:
+  }
+\prg_new_conditional:Npnn \flag_test:c #1 { p , T , F , TF }
+  {
+    \if_cs_exist:w #1 \cs_end:
+      \prg_return_true:
+    \else:
+      \prg_return_false:
+    \fi:
+  }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}[EXP]{\flag_raise:N, \flag_raise:c}
+%   Raising a flag expandably relies on the fact that \TeX{}
+%   automatically lets undefined control sequences to \tn{relax}
+%   when building an unknown csname. We build such a csname, then
+%   remove it with \cs{use_none:n}, essentially doing
+%   \cs{use_none:c}, but optimized slightly. When a flag is given
+%   as an \texttt{N}-type argument, a little more work is needed,
+%   converting to a csname before raising that.
+%    \begin{macrocode}
+\cs_new:Npn \flag_raise:N #1
+  { \exp_after:wN \use_none:n \cs:w \cs_to_str:N #1 \cs_end: }
+\cs_new:Npn \flag_raise:c #1
+  { \exp_after:wN \use_none:n \cs:w #1 \cs_end: }
+%    \end{macrocode}
+% \end{macro}
+%
+% \begin{macro}{\flag_lower:N, \flag_lower:c}
+%   Simply undefine the control sequence, locally.
+%    \begin{macrocode}
+\cs_new_protected:Npn \flag_lower:N #1
+  { \cs_set_eq:NN #1 \c_undefined:D }
+\cs_generate_variant:Nn \flag_lower:N { c }
+%    \end{macrocode}
+% \end{macro}
+%
+%    \begin{macrocode}
+\msg_kernel_new:nnnn { flag } { already-defined }
+  { The~control~sequence~#1~is~already~declared~as~a~flag. }
+  {
+    LaTeX~was~asked~to~define~the~flag~#1,~but~it~has~already~
+    been~defined~as~a~flag.~The~flag~module~is~mostly~meant~
+    for~kernel~use,~and~booleans~should~be~preferred.
+  }
+%    \end{macrocode}
+%
+%    \begin{macrocode}
+%</initex|package>
+%    \end{macrocode}
+%
+% \end{implementation}
+%
+% \PrintIndex
-- 
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