How to check the existence of some characters in a font using a loop?

Question

I am trying to modify the current version of xepersian package to suit my needs. The following code copied from xepersian-mathsdigitspec.sty is supposed to check if some characters do exist in the font to be loaded. My question is about the function \__xepersian_mathsdigitspec_char_not_exist_error. Is there any way to replace those repeating lines of code in the argument of the function with a (while, until, ...) LOOP which iterates over a list of characters [06F0, ..., 066B]?

\cs_new:Npn \__xepersian_mathsdigitspec_error:nxx    { \msg_error:nnxx    {xepersian-mathsdigitspec} }
\cs_new:Nn \__xepersian_mathsdigitspec_msg_new:nnnn
  { \msg_new:nnxx {#1} {#2} { \tl_trim_spaces:n {#3} } { \tl_trim_spaces:n {#4} } }
\char_set_catcode_space:n {32}
\__xepersian_mathsdigitspec_msg_new:nnnn {xepersian-mathsdigitspec} {char-not-exist}
 {
  The font "#1" does not contain U+#2.
 }
 {
  Select another font and rerun xelatex.
 }
\char_set_catcode_ignore:n {32}

\prg_new_conditional:Nnn \__xepersian_mathsdigitspec_primitive_font_char_if_exist:n {p,TF,T,F}
  {
    \etex_iffontchar:D \l_fontspec_font `#1 \scan_stop:
      \prg_return_true:
    \else:
      \prg_return_false:
    \fi:
  }

\cs_new:Nn \__xepersian_mathsdigitspec_char_not_exist_error:n
 {
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۰ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F0 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۱ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F1 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۲ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F2 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۳ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F3 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۴ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F4 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۵ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F5 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۶ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F6 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۷ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F7 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۸ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F8 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۹ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F9 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ٫ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 066B } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ٪ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 066A } }
 }

Answer 1

After reading the documents "The expl3 package and LaTeX3 programming" and the "LaTeX3 Interfaces" again (but thoroughly this time) I think I have found a solution to my question. I replaced the following piece of code in xepersian-mathsdigitspec.sty:

\prg_new_conditional:Nnn \__xepersian_mathsdigitspec_primitive_font_char_if_exist:n {p,TF,T,F}
  {
    \etex_iffontchar:D \l_fontspec_font `#1 \scan_stop:
      \prg_return_true:
    \else:
      \prg_return_false:
    \fi:
  }

\cs_new:Nn \__xepersian_mathsdigitspec_char_not_exist_error:n
 {
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۰ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F0 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۱ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F1 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۲ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F2 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۳ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F3 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۴ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F4 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۵ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F5 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۶ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F6 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۷ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F7 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۸ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F8 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ۹ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 06F9 } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ٫ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 066B } }
    \__xepersian_mathsdigitspec_primitive_font_char_if_exist:nF ٪ { \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #1 } { 066A } }
 }

with

\seq_new:N \l_my_xepersian_digits_seq 
\seq_set_split:Nnn \l_my_xepersian_digits_seq { , } { 06F0 , 06F1 , 06F2 , 06F3 , 06F4 , 06F5 , 06F6 , 06F7 , 06F8 , 06F9 , 066A , 066B }

and replaced all instances of the function \__xepersian_mathsdigitspec_char_not_exist_error with:

\seq_map_inline:Nn \l_my_xepersian_digits_seq
  {
    \etex_iffontchar:D \l_fontspec_font "##1 \scan_stop:
    \else:
      \__xepersian_mathsdigitspec_error:nxx {char-not-exist} { #2 } { ##1 }
    \fi:
  }

Of course one can use \seq_map_function to define a new function and replace all occurrences of the function \__xepersian_mathsdigitspec_char_not_exist_error with that.