<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><font size="5" class="">The code </font><div class=""><br class=""><div class=""><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\begin{equation}</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\boldsymbol [ \c_b, \c_c \boldsymbol ]^\dag</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">={} [ \c_c^\dag, \c_b^\dag ]</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">= \left\{</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\begin{array}{ll}</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">- \boldsymbol [ \c_b, \c_c \boldsymbol ] & </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\mbox{ for } b, c = 1, 2, 3 \\</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\boldsymbol [ \c_b, \c_c \boldsymbol ] & </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\mbox{ if } b \mbox{ or } c = 0 . </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\end{array} </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\right .</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\end{equation} </div></div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">works, but the nearly identical code</div></div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"><div class="" style="font-size: 18px;"><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\begin{equation}</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\boldsymbol [ \c_b, \c_c \boldsymbol ]^\dag</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">={} [ \c_c^\dag, \c_b^\dag ]</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">= \left\{</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\begin{array}{ll}</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">- \boldsymbol [ \c_b, \c_c \boldsymbol ] & </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\mbox{ for } b, c = 1, 2, 3 \\</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">[ \c_b, \c_c ] & </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\mbox{ if } b \mbox{ or } c = 0 . </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\end{array} </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\right .</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">\end{equation} </div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">does not;</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">the error message is</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"><br class=""></div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">418: Illegal unit of measure (pt inserted).</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"><to be read again></div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"> _</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">l. 418 [ \c_b, \c_c ]</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;"> &</div><div class="" style="margin: 0px; font-stretch: normal; font-size: 24px; line-height: normal;">?</div></div></div></body></html>