fortran - Calling function with configurable real precision -

the goal:

have function work configurable working precision.

when try this:

program vierkantsvergelijking implicit none  integer, parameter :: dp = kind(0.d0) integer, parameter :: sp = kind(0.0)  print *, algoritme1(-5771.,2.,dp) contains    function algoritme1(b,c,wp) result( solution)     integer :: wp ! working precision     real(kind=wp) :: b,c,d     real(kind=wp), dimension(2) :: solution     d = sqrt((b/2)**2 - c)     solution(1) = -b/2 + d     solution(2) = -b/2 - d   end function algoritme1  end program 

i get: error: type mismatch in argument 'b' @ (1); passed real(4) unknown

why not working , how can achieve goal?

yes, or rather no, that's not going work, not no how. intel fortran compiler complains, line:

real(kind=wp) :: b,c,d 

that

a kind type parameter must compile-time constant.   [wp] 

it makes same complaint real(kind=wp), dimension(2) :: solution too. deep-rooted feature of fortran.

to want have define generic interface, along these lines

interface algoritme1     procedure :: algoritme1_sp, algoritme1_dp end interface 

and write code both procedures. compiler can determine 1 called function signature; presumably 1 have sp arguments, other dp arguments.

you might think means fortran doesn't generic procedures, i'll leave question sophists , language nit-pickers. worth while search around generic programming in fortran; here on there tricks , tips on how better avoid writing multiple implementations of programmer believes (at odds compiler) 'same' code.