Am Thu, 4 Aug 2011 17:46:40 +0100 schrieb Joseph Wright: >> l3basics contains \luatex_if_engine:... and \xetex_if_engine:... >> I would find similar \xetex_or_luatex_if_engine: > I think you are after '\pdftex_if_engine:', as this deals with the case > where the engine is pdfTeX or otherwise. You mean \pdftex_if_engine will give true for all engines with the exception of xetex + luatex? Even with etex or omega? In this case it is what I'm after. But why does nobody use it? E.g. siunitx contains \xetex_if_engine:F { \luatex_if_engine:F.... -- Ulrike Fischer