% This file is part of the CTAN package named ifis-macros.
%
% gluecomp.tex: a) provide macro \makeTsgm to store a glue specification as
% a ``TeX split glue macro'' (Tsgm)
% b) provide macros \ifnatwd, \ifstretch, and \ifshink to check
% the components of two glue specifications stored as Tsgms.
%
%
% Usage: a) \makeTsgm <glue specification>!<control sequence>
% and <control sequence> is defined as the Tsgm.
% b) \ifnatwd | \ifstretch | \ifshrink
% <argument1><relation><argument2>\Boolend
% <true branch>\else <false branch>\fi
% where <relation> is < | = | >
%
% Copyright (C) 2025 Udo Wermuth (author)
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
%
\input ifisglue.tex
\catcode`\@=11
%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%% PART I: TeX split glue macro (Tsgm)
%%%
% interpret \II@sto & \II@sho from ifisglue.tex
\def\II@getorder #1{% #1: \II@sto or \II@sho
\ifx#1\empty 0 \else\ifx#1\II@l 1
\else\ifx#1\II@ll 2 \else 3 \fi\fi\fi}
%
% TSGM MACRO 1:
% convert input to a Tsgm (TeX split glue macro)
%
\def\makeTsgm #1!#2{% #1: glue; #2: name of Tsgm
\ifcat\relax\noexpand#2%can #2 be a macro name?
\expandafter\ifisglue #1\Boolend %must be true
{\ifIImuglue\muskip255\else\skip255\fi=#1%
\xdef\II@glue{\ifIImuglue\the\muskip255
\else\the\skip255\fi}}% TeX canonical form
\expandafter\ifisglue\II@glue\Boolend
\edef#2##1{\noexpand\ifcase##1 % create Tsgm
\ifIImuglue1 \else0 \fi\noexpand\or %0:type
\II@nw\noexpand\or % 1: natural width
\ifx\II@st\space 0pt \else\II@st\fi % 2 and
\noexpand\or \II@getorder\II@sto %3:stretch
\noexpand\or
\ifx\II@sh\space 0pt \else\II@sh\fi % 4 and
\noexpand\or \II@getorder\II@sho %5: shrink
\noexpand\or \II@glue\noexpand\or %6: value
314.271\noexpand\else cm\noexpand\fi}\fi%id
\else\errhelp{A glue specification should have
been here; I replaced your input by `0pt' to
build the Tsgm.}\II@setzero #2%
\errmessage{Missing glue, treated as zero}\fi
\else \errhelp{The argument after `!' must be a
control sequence that I can define/redefine.
Proceed; I'll ignore the \makeTsgm I just
read.}%
\errmessage{Invalid name for new macro}\fi}
%
\def\II@setzero #1{% #1: Tsgm name for zero skip
\def#1##1{\ifcase##1 0 \or 0pt % type and natwd
\or 0pt \or 0 \or 0pt \or 0 % stretch & shrink
\or 0.0pt \or 314.271\else cm\fi}}%glue and id
% access components of a Tsgm
\def\II@gluetype #1{#10 }% the argument #1 is
\def\II@natwd #1{#11 }% in all these macros
\def\II@stretchdim #1{#12 }% a valid Tsgm, i.e.,
\def\II@stretchord #1{#13 }% it's a control word
\def\II@shrinkdim #1{#14 }% filled by the macro
\def\II@shrinkord #1{#15 }% \makeTsgm
%
% TSGM MACRO 2:
% check that a macro is a Tsgm
%
\def\ifIIisTsgm #1\Boolend{%compare to \ifisglue
\wlog{=+= start ignore}\batchmode\begingroup
\setbox0=\hbox{\dimen255=0#17cm
\ifdim\dimen255=314.271#1{-1}\else 0\fi}%
\xdef\II@wd{\the\wd0 }\endgroup\IIcurrentmode
\wlog{=+= stop ignore}\ifdim\II@wd=0pt }
%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%
%%% PART II: componentwise comparisions
%%%
%
% USER MACROS 1--3:
% compare two corresponding components of Tsgms
%
% macro arguments #1,#3: Tsgm; #2: relation
\def\ifnatwd #1#2#3\Boolend{\II@sofarfalse %init
\ifIIisTsgm#1\Boolend \ifIIisTsgm#3\Boolend
\ifnum\II@gluetype#1=\II@gluetype#3%test types
\else \II@badtypes \fi % used muglue and glue
\II@chkrel#2{\string\ifnatwd}% check relation
\ifdim\II@natwd#1\II@rel\II@natwd#3%
\II@sofartrue \fi
\else\II@noTsgm2\fi \else\II@noTsgm1 % bad Tsgm
\fi \ifII@sofar}
\def\ifstretch #1#2#3\Boolend{\II@sofarfalse
\ifIIisTsgm#1\Boolend \ifIIisTsgm#3\Boolend
\ifnum\II@gluetype#1=\II@gluetype#3%test types
\else \II@badtypes \fi % used muglue and glue
\II@chkrel#2{\string\ifstretch}% test relation
\ifnum\II@stretchord#1=\II@stretchord#3\relax
\ifdim\II@stretchdim#1\II@rel % compare dimen
\II@stretchdim#3\relax \II@sofartrue \fi
\else\ifnum\II@stretchord#1\II@rel
\II@stretchord#3\relax \II@sofartrue \fi\fi
\else\II@noTsgm2\fi \else\II@noTsgm1 % bad Tsgm
\fi \ifII@sofar}
\def\ifshrink #1#2#3\Boolend{\II@sofarfalse
\ifIIisTsgm#1\Boolend \ifIIisTsgm#3\Boolend
\ifnum\II@gluetype#1=\II@gluetype#3%test types
\else \II@badtypes \fi % used muglue and glue
\II@chkrel#2{\string\ifshrink}% test relation
\ifnum\II@shrinkord#1=\II@shrinkord#3\relax
\ifdim\II@shrinkdim#1\II@rel % compare dimen
\II@shrinkdim#3\relax \II@sofartrue \fi
\else\ifnum\II@shrinkord#1\II@rel
\II@shrinkord#3\relax \II@sofartrue \fi\fi
\else\II@noTsgm2\fi\else \II@noTsgm1 % bad Tsgm
\fi \ifII@sofar}
%
% Error messages
\def\II@noTsgm #1{% #1: 1 or 2 to select 1st/3rd
\errhelp{I expected a macro with a special
structure. But the received argument does not
obey this structure. I cannot perform the test
and return false.}\errmessage{Not a TeX split
glue macro (\ifodd#1 1st \else 3rd \fi arg.)}}
\def\II@chkrel #1#2{% #1: character; #2: caller
\def\II@rel{#1}% save the relation
\if#1<\else\if#1=\else\if#1>\else
\errhelp{I was expecting to see `<', `=', or
`>'. Didn't.}\def\II@rel{=}% replace relation
\errmessage{Missing = inserted for #2}%
\fi\fi\fi}
\def\II@badtypes{\errhelp{I'm going to assume
that 1mu=1pt when they're mixed.}%
\errmessage{Incompatible glue units}}
\catcode`\@=12