Defining a variable that must be declared constant, but changes in a loop

Question

I\'m testing out ranges of values (-1:34 just for kicks) for the function selected_real_kind to determine the kind parameter it returns and the actual

Answer 1

Similar to george's answer, but in Fortran. We note that kinds are something that, essentially, must be known at compile-time. For that we ask the compiler which kinds it can offer us and, for each of those, create a small chunk of code to be compiled. Then compile and run it. [This last step certainly varies by system.]

! Rather than looping over a range with SELECTED_REAL_KIND, just see which
! real kinds are available to the compiler.  We can later match up real kinds
! for a requested precision with those here.
  use, intrinsic :: iso_fortran_env, only : real_kinds
  implicit none

  integer output
  integer i

  open(newunit=output, file='gosh.f90', action='write', position='rewind')

! Here we could instead do n=-1, 34 etc.
  do i=1, SIZE(real_kinds)
     write(output, 1) real_kinds(i)
  end do

  write(output, '("end")')
  close(output)

! A compile/execute line - do whatever is required.
  call execute_command_line('compile gosh.f90 && ./a.out')

1 FORMAT ("block",/,"real(",I0,") x",/,"include 'domystuffz'"/,"end block")

end

where "domystuffz" is a file containing whatever analysis is wanted. As with High Performance Mark's answer something intrinsic would be nice and the include could be replaced by some simple code if required.