# Re: [NTG-context] Unexpected emergency stop



Tim Steenvoorden <mailto:tim.steenvoor...@gmail.com>
10. Februar 2018 um 12:44
Thanks Otared! Works like a charm!


Out of curiosity, could you explain the mechanics behind this? I know it is a commonly used trick in TeX macro definitions, but I don’t know how it changes TeX’s understanding of the tokes it parses.

When you create a new commands like this

\def\mycommand[#1]{...}


the brackets are delimiters for the argument of the command, i.e. when TeX sees \mycommand it looks for [ and grabs everything intill ] as as argument. When you out now a space (or start a new line) after ] in your definition of the command, e.g.

\def\mycommand[#1] {...}

TeX looks now for “] ” (right bracket followed by a space) as delimiter for

Wolfgang

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