--- a/data.sty	Wed Oct 07 09:08:55 2020 +0100
+++ b/data.sty	Sun Oct 11 09:10:08 2020 +0100
@@ -73,6 +73,21 @@
 28 34.79653
 \end{filecontents}
 
+%% example a?{n} a{n}
+\begin{filecontents}{re-rust.data}
+1000 0.95
+1500 2.17  
+2000 3.9
+2100 4.121
+2150 4.3
+2180 14.9
+2200 15  
+2500 18  
+3000 24
+3500 31
+4000 40
+\end{filecontents}
+
 % JavaScript, example (a*)*b  
 \begin{filecontents}{re-js.data}
 5   0.061