How can I change the default order between letters of an alphabet?

Question

I'm writing a book in Persian. In its index there is a problem. Words are using Arabic order! So it causes a problem as in Arabic language they don't have four letters 'پ p (in pen)', 'چ ch (in cheese)', 'گ g (in gas)' and 'ژ zh or s (in usual)'. So these 4 letters are deleted from their main places and these are appeared after all letters but it's wrong, for example 'پ p' should be after 'ب b' and before 'ت t'. I would to see can I define order between letters of an alphabet myself. So I'm not only seeking a solution for the above problem and my question is the generalized form of it (the general case may be useful sometimes).

As some may need an example I wrote one (this is just an example).

\documentclass[12pt,a4paper]{article}
\usepackage[next]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{makeidx}
\usepackage[left=2.00cm, right=2.00cm, top=2.00cm, bottom=1.50cm]{geometry}
\usepackage{xepersian}
\settextfont{XB Niloofar}
\author{A.H. SadeghiManesh}
\makeindex
\begin{document}
نمونه
\index{بالارونده}
\index{پائین‌رونده}
\index{تعمیم قضیه}
\printindex
\end{document}

The result is as the image. but the third word should be between two others and not the last one!

Answer 1

Judging from the output, I guess you use xelatex file.tex, then makeindex file.idx, and finally xelatex file.tex again. This won’t work, as makeindex isn’t so language-aware.

You can use xindy (xindy) for the middle step instead, with the support for Persian being provided by xindy-persian. The easiest way would be downloading xindy-persian to the sub-directory below the one your .tex file is in, and using texindy -M xindy-persian/variant1-utf8-test.xdy file.idx (you can also use variant2, which is slightly different (see README), or change -test with -lang).

Here is the output; I hope this is what you were expecting.