\dimen@??がうまく使えない

名前: tommy_minor
日時: 2007-11-08 22:14:10
IPアドレス: 210.167.83.*

またまた理解に苦しむ現象が生じたので質問いたします．
行の順番を変えると，\dimen@??に代入した数値がおかしくなるのです．
当方の環境では以下のようになります．
emath掲示板で同じ質問をして，取り敢えずの解決策を頂きましたが．
何故こんなことがおこるのでしょうか？
トーシローは\dimen@??なんか使っちゃだめ，ということなのでしょうか．

\documentclass[fleqn]{jarticle}
\usepackage{calc}

\begin{document}
\makeatletter
\settoheight{\dimen@}{$\mathstrut$}%
\settodepth{\dimen@i}{$\mathstrut$}%
\settoheight{\dimen@ii}{$\mathstrut$}%
$D_0=\the\dimen@,~D_1=\the\dimen@i,~D_2=\the\dimen@ii.$
% OK 7.5, 2.5, 7.5

\settoheight{\dimen@}{$\mathstrut$}%
\settoheight{\dimen@ii}{$\mathstrut$}%
\settodepth{\dimen@i}{$\mathstrut$}%
$D_0=\the\dimen@,~D_1=\the\dimen@i,~D_2=\the\dimen@ii.$
% NG 7.5, 2.5, 2.5

\settodepth{\dimen@i}{$\mathstrut$}%
\settoheight{\dimen@}{$\mathstrut$}%
\settoheight{\dimen@ii}{$\mathstrut$}%
$D_0=\the\dimen@,~D_1=\the\dimen@i,~D_2=\the\dimen@ii.$
% OK 7.5, 2.5, 7.5

\settodepth{\dimen@i}{$\mathstrut$}%
\settoheight{\dimen@ii}{$\mathstrut$}%
\settoheight{\dimen@}{$\mathstrut$}%
$D_0=\the\dimen@,~D_1=\the\dimen@i,~D_2=\the\dimen@ii.$
% OK 7.5, 2.5, 7.5

\settoheight{\dimen@ii}{$\mathstrut$}%
\settoheight{\dimen@}{$\mathstrut$}%
\settodepth{\dimen@i}{$\mathstrut$}%
$D_0=\the\dimen@,~D_1=\the\dimen@i,~D_2=\the\dimen@ii.$
% NG 7.5, 2.5, 2.5

\settoheight{\dimen@ii}{$\mathstrut$}%
\settodepth{\dimen@i}{$\mathstrut$}%
\settoheight{\dimen@}{$\mathstrut$}%
$D_0=\the\dimen@,~D_1=\the\dimen@i,~D_2=\the\dimen@ii.$
% OK 7.5, 2.5, 7.5

\makeatother
\end{document}

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