let stdl, altl and arev throw errors outside of pdfTeX

Doc/tex/doc_MRTfonts.tex

@@ -94,10 +94,12 @@ giving a uniform look to the documents.
 \section{Macros}\label{sec:fonts:macros}
 %>>=
 \begin{describemacro}{stdl}
+  \emph{Only available in \hologo{pdfTeX}.}\\
   \cs{stdl} will result in the lower case |l| from the \pkg{helvet} font in
   maths (\bverb|$\stdl$| results in $\stdl$).
 \end{describemacro}
 \begin{describemacro}{altl}
+  \emph{Only available in \hologo{pdfTeX}.}\\
   \cs{altl} provides an alternative lower case |l| for use in maths which is
   distinct from an upper case |I|. Compare: $\stdl I$ (that is |$\stdl I$|) and
   $\altl I$ (that is |$\altl I$|). There is no bold version of \cs{altl}
@@ -105,6 +107,7 @@ giving a uniform look to the documents.
   standard fonts will be the ones used there.
 \end{describemacro}
 \begin{describemacro}{arev}[\marg{symbols}]
+  \emph{Only available in \hologo{pdfTeX}.}\\
   This is another maths font (similar to \cs{mathbf} or \cs{mathcal}), that will
   use the maths font of \pkg{arevmath}, from which \cs{altl} is taken. Take a
   look at the following (the first group uses the standard maths fonts, the

Doc/tex/doc_MRTsfacc.tex

@@ -42,7 +42,7 @@ The package has the following options:
   redefine \cs{mathaccentV} or the definition has changed but you're sure that
   \pkg{MRTsfacc} still works with (it redefines it anyway) you can deactivate
   that test with this option. If \pkg{amsmath}'s definition of \cs{mathaccentV}
-  has changed, please contact the me as described in \autoref{sec:bugs}.
+  has changed, please contact the maintainer as described in \autoref{sec:bugs}.
 \end{describeopt}
 
 Every other option is passed on to \cs{MRTsfaccSet}, its description is included

MRTfonts/MRTfonts.sty

@@ -1,5 +1,5 @@
-\newcommand*\MRTfonts@version{0.0.8}
-\newcommand*\MRTfonts@date{2020-08-01}
+\newcommand*\MRTfonts@version{0.0.9}
+\newcommand*\MRTfonts@date{2020-10-18}
 
 \NeedsTeXFormat{LaTeX2e}
 
@@ -212,7 +212,35 @@
 
 %% alternative lower case l for maths >>=
 %%=============================================================================
-\bool_if:NF \c_MRTfonts_xetex_or_luatex_bool
+\bool_if:NTF \c_MRTfonts_xetex_or_luatex_bool
+  {
+    \MRTutil@def[\long]\arev#1
+      {
+        \msg_error:nnnn { MRTfonts } { wrong~engine }
+          { macro ~ `\arev' } { pdftex }
+        #1
+      }
+    \MRTutil@def\stdl
+      {
+        \msg_expandable_error:nnnn { MRTfonts } { wrong~engine }
+          { macro ~ `\stdl' } { pdftex }
+        l
+      }
+    \MRTutil@def\altl
+      {
+        \msg_expandable_error:nnnn { MRTfonts } { wrong~engine }
+          { macro ~ `\altl' } { pdftex }
+        l
+      }
+    \AtBeginDocument
+      {
+        \cs_if_exist:NT \MRTsfaccShift
+          {
+            \MRTsfaccShiftLet \stdl l
+            \MRTsfaccShiftLet \altl l
+          }
+      }
+  }
   {
     \DeclareSymbolFont{AREVletters}{OML}{zavm}{m}{it}
     \DeclareSymbolFontAlphabet{\arev}{AREVletters}