On Sat, 9 Nov 2013, Peter Münster wrote:

> Hi,
>
> How could I avoid that error here please:
>
> --8<---------------cut here---------------start------------->8---
> \def\beginInvoice{\dosingleempty\dobeginInvoice}
> \def\dobeginInvoice[#1]{\grabbufferdata[myLetter][beginInvoice][endInvoice]}
> \def\startInvoice#1\stopInvoice{bla}
> \starttext
> \beginInvoice
> \startInvoice test \stopInvoice
> \endInvoice
> \stoptext

One possibility is to restrict optional arguments to one line:

\def\beginInvoice{\bgroup\obeylines\dosingleempty\dobeginInvoice}
\def\dobeginInvoice[#1]{\egroup\grabbufferdata[myLetter][beginInvoice][endInvoice]}

Aditya