!  A simple interactive demo program
 !  ------------------------------------------------
 !  Note the use of file units "fin" (Fortran input)
 !  and "fout" (Fortran output).  These are aliases
 !  for the "5" and "6" Logical Unit Numbers (LUNs).
 !  These LUN asignments are not mentioned in any
 !  Fortran standard but are probably supported by
 !  all F90 compilers, for historical reasons.
 !
 !  Input/Output is cumbersome in SEA because there
 !  is no Fortran builtin IO mechanism for derived
 !  types (unlike e.g. Pascal) and the IO statements
 !  cannot be overloaded.

 program test
   use sea_arithmetic                             !  Error analytic module
   type(sea_abs)  :: x, y, z                      !  Declare our vars

   call sea_check_precise()                       !  Verify PRECISE reals exist

   call sea_read_abs(fin, x, "Enter |x,e|>: ")    !  Input X
   call sea_read_abs(fin, y, "Enter |y,e|>: ")    !  Input Y
   call sea_write_nl(fout)                        !  Write a newline

   call sea_write_txt_nl(fout, "# the input: ")   !  Write a line of text

   call sea_write_entry(fout, "x = ", x, 5)       !  Write number
   call sea_write_entry(fout, "y = ", y, 5)       !  Write number
   call sea_write_nl(fout)                        !  Write a newline

   call sea_write_txt_nl(fout, "# z = x / x")     !  Write a line of text
   z = x / x                                      !  Error analytic division
   call sea_write_entry(fout, "x/x = ", z, 5)     !  Write result
   call sea_write_nl(fout)                        !  Write a newline

   call sea_write_txt_nl(fout, "# z = x / y")     !  Write a line of text
   z = x / y                                      !  Error analytic division
   call sea_write_entry(fout, "x/y = ", z, 5)     !  Write result
   call sea_write_nl(fout)                        !  Write a newline
                                                  !
   ! SEA_DEBUG = 1                                !  Check SIN algorithm
                                                  !
   call sea_write_txt_nl(fout, "# trigo... ")     !  Write a line of text
   z = sin(x)                                     !  Error analytic sin(x)
   call sea_write_entry(fout, "sin(x) = ", z, 5)  !  Write sin(x)
   z = cos(x)                                     !  Error analytic cos(x)
   call sea_write_entry(fout, "cos(x) = ", z, 5)  !  Write cos(x)
   z = tan(x)                                     !  Error analytic tan(x)
   call sea_write_entry(fout, "tan(x) = ", z, 5)  !  Write tan(x)
   z = alt_tan(x)                                 !  Compute alt-tan(x)
   call sea_write_entry(fout, "alt-tan  ", z, 5)  !  Write alt-tan(x)
   call sea_write_nl(fout)                        !  Write a newline

 end program test