# [NTG-context] Bad interaction between new interpretation of underscore and modules

Thu Jan 13 22:50:06 CET 2011

Am 13.01.2011 um 17:18 schrieb Mathieu Boespflug:

> Hi all,
>
> today's beta introduced a really strange problem. Consider two source files:
>
> definitions.tex:
> \startmodule[definitions]
> \def\lambdax{\lambda_x}
> \stopmodule[definitions]
>
> main.tex:
> \usemodule[definitions]
> \starttext
> blah $\lambdax$ blah.
> \stoptext
>
> This results in the following compile error:
>
> ! Undefined control sequence.
> \lambdax ->\lambda_x
>
> l.5 blah $\lambdax >$ blah.
> ?
>
> However, if you change "\usemodule[definitions]" into "\input
> definitions" instead, then there is no compile error! My understanding
> is that the underscore is a valid character for macro names now
> outside of math mode, which is what is causing the problem. But I
> really don't understand what magic is going on in the modules code to
> trigger this.
>
> I would be very interested in an explanation of what is going on.

You need \normalsubscript in your module. You define a command and
in this case it doesn’t matter that you plan to use it in math mode,
the _ is now a normal letter like “a” and this won’t change when you