{Clear the screen and display a title}
display_title(+++ Inverse Position Problems +++)

{Set default values for first pass}
if (s1=.)
   
{First ask for the controlling parameters}
   set_string(s1,10)
   ask_for_string(Maximum step size [days],s1)
   set_maximum_step(s1)

   set_string(s1,100)
   ask_for_string(Maximum number of steps in the search,s1)
   set_number_of_iterations(s1)

   set_string(s1,1e-6)
   ask_for_string(Tolerance,s1)
   set_tolerance(s1)

   new_line
   write_string(Allowed coordinate types are true, apparent, and topocentric)
   new_line
   set_string(s1,true)
   ask_for_string(Type of coordinates to be used,s1)
   set_coordinates_type(s1)
   new_line 

{Now set the defaults for the find_when command}
   set_string(s1,Sun)
   set_string(s2,hour angle)
   set_string(s3, )
end_if

{Get the first argument}
write_string(Valid first arguments are:)
new_line
write_string(--------------------------)
new_line
new_line
write_string(Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune,)
new_line
write_string(Elliptical, Parabolic, or name of body with current RA and Dec)
new_line
new_line
ask_for_string(First argument [choose one of the above],s1)

{Get coordinates if not a main body: added after printing book!}
if (s1!Sun)
 if (s1!Moon)
  if (s1!Mercury)
   if (s1!Venus)
    if (s1!Mars)
     if (s1!Jupiter)
      if (s1!Saturn)
       if (s1!Uranus)
        if (s1!Neptune)
         if (s1!parabolic)
          if (s1!elliptical)
           ask_for_coordinates(r)
          end_if
         end_if
        end_if
       end_if
      end_if
     end_if
    end_if
   end_if
  end_if
 end_if
end_if

{Get the second argument}
new_line
write_string(Valid second arguments are:)
new_line
write_string(---------------------------)
new_line
new_line
write_string(Hour angle, Right ascension, Declination, Azimuth, Altitude,)
new_line
write_string(Ecliptic longitude, Ecliptic latitude, Galactic longitude,)
new_line
write_string(Galactic latitude, conjunction in el, conjunction in ra,) 
new_line
write_string(opposition in el, or opposition in ra)
new_line
new_line
ask_for_string(Second argument [choose one of the above],s2)
new_line

{Discriminate between the two variants of the find_when command}
set_character(c1,A)
if (s2=conjunction in ra)
   set_character(c1,B)
end_if
if (s2=conjunction in el)
   set_character(c1,B)
end_if
if (s2=opposition in ra)
   set_character(c1,B)
end_if
if (s2=opposition in el)
   set_character(c1,B)
end_if

{Get the third argument according to find_when variant}
if (c1=A)
   ask_for_string(Target value,s3)
end_if
if (c1=B)
ask_for_string(Second object name [Sun/Moon/Venus etc.],s3)
end_if

{Perform the calculation, and display the result}
new_line
find_when(s1,s2,s3)

{Another go?}
new_line
ask_for_repeat