Arabic with Exam class: Incompatible?

Question

I am trying to use the polyglossia package to write exams in Arabic with the Exam documentclass, as can be seem in the following MWE. I ended up however with an error :

! Missing number: Treated as Zero.

< to be read again>

1.32 \question[5]

\documentclass[addpoints,12pt]{exam}
\usepackage[no-math]{fontspec}
\usepackage[quiet]{polyglossia}
\usepackage{amsmath,amsthm,amsfonts}
\usepackage{amssymb}
\usepackage{fontspec}% هذه لنستطيع تغيير الخطوط

\setdefaultlanguage{arabic}
\setotherlanguage[variant=british]{english}
\setmainfont{Simplified Arabic}
\setromanfont{Arial}
\defaultfontfeatures{Scale=MatchLowercase}
\setmonofont{Simplified Arabic}
\setsansfont{Junicode}
\newfontfamily\arabicfont[Script=Arabic,Scale=1]{Amiri}
\newfontfamily\arabicfonttt[Script=Arabic,Scale=1.3]{Times New Roman}
\newcommand{\eng}{\textenglish}

\begin{document}
\pagestyle{headandfoot}
\firstpageheadrule
\firstpageheader{Name:} { } {مادة}
\firstpagefooter{}{الإختبار النهائي}
{}
\runningheader{Name:} { } {مادة}
\runningfooter{}{الإختبار النهائي}
{}
\runningheadrule
\runningfootrule

\begin{questions}
\question[5]
عرف الدالة؟
\\
\hrulefill
\question
أثبت أن
\end{questions}
\end{document} 

Edit:

Here is another trial using the babel package. The only problem now is that the grading table is not shown correctly; it is shown in the reverse order.

\documentclass[11pt]{exam}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[arabic]{babel}

\makeatletter
\newcommand\point@labelone{درجة}
\newcommand\point@labeltwo{درجتان}
\newcommand\point@labelthree{درجات}
\newcommand\point@labelfour{درجات}


\renewcommand\points{%
  \begingroup
    \let\half=\relax
    \edef\pt@string{\@points}%
    \ifthenelse{\equal{\pt@string}{1} \OR \equal{\pt@string}{\half}}
    {\point@labelone}{%
    \ifthenelse{\equal{\pt@string}{2}}{\point@labeltwo}{%
    \ifthenelse{\equal{\pt@string}{3} \OR \equal{\pt@string}{3\half}%
    \OR \equal{\pt@string}{4} \OR \equal{\pt@string}{4\half}%
    \OR \equal{\pt@string}{5} \OR \equal{\pt@string}{5\half}%
    \OR \equal{\pt@string}{6} \OR \equal{\pt@string}{6\half}%
    \OR \equal{\pt@string}{7} \OR \equal{\pt@string}{7\half}%
    \OR \equal{\pt@string}{8} \OR \equal{\pt@string}{8\half}%
    \OR \equal{\pt@string}{9} \OR \equal{\pt@string}{9\half}%
    \OR \equal{\pt@string}{10}\OR \equal{\pt@string}{10\half}}
     {\point@labelthree}{\point@labelfour}}}
          %
  \endgroup
}

\renewcommand\thepoints{%
  \if@placepoints
    \if@bonus
      \@points \@bonuspointname
    \else
    \let\half=\relax
    \edef\pt@string{\@points}%
    \ifthenelse{\equal{\pt@string}{1} \OR \equal{\pt@string}{\half}%
                                      \OR \equal{\pt@string}{2}}
    {\@pointname}{\@points \@pointname}
     \fi
  \fi
}% thepoints

\makeatother

\pointformat{(\thepoints)}


\begin{document}
{
\centering
\vspace{0pt}
\gradetablestretch{2}
\vpword{نقاط}
\vtword{المجموع:}
\vsword{الدرجة}
    \addpoints % required here by exam.cls, even though questions haven't started yet.
{\small
    \gradetable[v]%[pages]  % Use [pages] to have grading table by page instead of question
}


\begin{questions}
\addpoints
\question[1] 
عرف الدالة الأسية.

\addpoints
\question[12] أوجد مشتقة الدالة $X^2 + \sin(x)$.

\addpoints
\question[12] ماهو نطاق الدالة السابقة؟

\end{questions}

\end{document} 

Answer 1

The class is buggy. It uses in various places formatting commands as numbers, and this breaks as soon as \@arabic no longer gives a number. An incomplete sample of problematic places:

\ifnum \thepageof@pagepoints > 0\relax
\ifnum \thepageof@pagebonuspoints > 0\relax
\ifnum \thepage > \PgInfo@get{@endquestions
\ifnum \thepage < \PgInfo@get{question@\thelatest@ques}\relax 
\ifnum \the@iterator < \tbl@lastp\relax    
\ifnum \theques@end > \thepage\relax 
\setcounter{next@ques}{\thelatest@ques}%

The class is full of them.

A simple example to break it is

\documentclass[addpoints,12pt]{exam}
\makeatletter\let\@arabic\@alph \makeatother

\begin{document}

\begin{questions}
\question[5]
blbuj
\end{questions}
\end{document} 

\pagenumbering{alph} is also enough to get errors. As it is it is completly unusable with arabic.

Answer 2

To resolve the issue of Arabic not shown correctly you can use \textRL as shown in the code.

\documentclass[11pt]{exam}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[arabic]{babel}


\makeatletter
\newcommand\point@labelone{\textRL{درجة}}
\newcommand\point@labeltwo{درجتان}
\newcommand\point@labelthree{درجات}
\newcommand\point@labelfour{درجات}


\renewcommand\points{%
  \begingroup
    \let\half=\relax
    \edef\pt@string{\@points}%
    \ifthenelse{\equal{\pt@string}{1} \OR \equal{\pt@string}{\half}}
    {\point@labelone}{%
    \ifthenelse{\equal{\pt@string}{2}}{\point@labeltwo}{%
    \ifthenelse{\equal{\pt@string}{3} \OR \equal{\pt@string}{3\half}%
    \OR \equal{\pt@string}{4} \OR \equal{\pt@string}{4\half}%
    \OR \equal{\pt@string}{5} \OR \equal{\pt@string}{5\half}%
    \OR \equal{\pt@string}{6} \OR \equal{\pt@string}{6\half}%
    \OR \equal{\pt@string}{7} \OR \equal{\pt@string}{7\half}%
    \OR \equal{\pt@string}{8} \OR \equal{\pt@string}{8\half}%
    \OR \equal{\pt@string}{9} \OR \equal{\pt@string}{9\half}%
    \OR \equal{\pt@string}{10}\OR \equal{\pt@string}{10\half}}
     {\point@labelthree}{\point@labelfour}}}
          %
  \endgroup
}

\renewcommand\thepoints{%
  \if@placepoints
    \if@bonus
      \@points \@bonuspointname
    \else
    \let\half=\relax
    \edef\pt@string{\@points}%
    \ifthenelse{\equal{\pt@string}{1} \OR \equal{\pt@string}{\half}%
                                      \OR \equal{\pt@string}{2}}
    {\@pointname}{\@points \@pointname}
     \fi
  \fi
}% thepoints

\makeatother

\pointformat{(\thepoints)}


\begin{document}
{
\centering
\vspace{0pt}
\gradetablestretch{2}
\vpword{\textRL{نقاط}}
\vtword{\textRL{المجموع:}}
\vsword{\textRL{الدرجة}}
    \addpoints % required here by exam.cls, even though questions haven't started yet.
{\small
    \gradetable[v]%[pages]  % Use [pages] to have grading table by page instead of question
}


\begin{questions}
\addpoints
\question[1] 
عرف الدالة الأسية.

\addpoints
\question[12] أوجد مشتقة الدالة $X^2 + \sin(x)$.

\addpoints
\question[12] ماهو نطاق الدالة السابقة؟

\end{questions}

\end{document}