Fail if we are not compiled by an ε-TeX compatible engine

diff --git a/ucwmac.tex b/ucwmac.tex
index 86dc5e5cc55840e3fa799645cfb0eef5ef855b72..a3d5f4dfe37cf4571b321895ec758fd7945adef6 100644 (file)
--- a/ucwmac.tex
+++ b/ucwmac.tex
@@ -1,5 +1,5 @@
 % The UCW Macro Collection (a successor of mjmac.tex)
-% Written by Martin Mares <mj@ucw.cz> in 2010--2013 and placed into public domain
+% Written by Martin Mares <mj@ucw.cz> in 2010--2018 and placed into public domain
 % -------------------------------------------------------------------------------
 
 %%% Prolog %%%
@@ -7,6 +7,10 @@
 % We'll use internal macros of plain TeX
 \catcode`@=11
 
+\ifx\eTeXversion\undefined
+\errmessage{ucwmac requires the e-TeX engine or its successor}
+\fi
+
 %%% PDF output detection %%%
 
 \newif\ifpdf