Dear list members, Why the following code gives me the following error? Code: \begingroup \catcode`\"=12 \gdef\newmcodes@{\mathcode`\'39\mathcode`\*42\mathcode`\."613A% \ifnum\mathcode`\-=45 \else \mathchardef\std@minus\mathcode`\-\relax \fi \mathcode`\-45\mathcode`\/47\mathcode`\:"603A\relax} \endgroup \definemathcommand[xyz][nolop]{\newmcodes@ \kern\zeropoint\mfunction{fancy-function-name'*.:}} \starttext $\xyz$ \stoptext Error: tex error > error on line 13 in file /Users/maggyero/Desktop/test.tex: ! Extended mathchar used as mathchar (4203026) <to be read again> = \newmcodes ...thcode `\."613A\ifnum \mathcode `\-= 45 \else \mathchardef \std... <argument> \newmcodes @ \kern \zeropoint \mfunction {fancy-function-name'*.:} \486>nolop #1->\mathop {#1 }\nolimits l.13 $\xyz $ Thank you in advance. Maggyero