Fortran Wiki
tostring

NAME

tostring(3f) - [M_tostring] converts any standard scalar type to a string

SYNOPSIS

function tostring(g1,g2.g3,g4,g5,g6,g7,g8,g9)

    class(*),intent(in),optional :: g1,g2,g3,g4,g5,g6,g7,g8,g9
    character,len=(:),allocatable :: tostring

DESCRIPTION

tostring(3f) builds a space-separated string from up to nine scalar values.

Requires modern Fortran. Shows an example of unlimited polymorphic arguments, optional arguments, and new forms of formats.

Tested with GNU Fortran 7.3.0.

OPTIONS

g[1-9]

optional value to convert to a string. May be of type INTEGER, LOGICAL, REAL, DOUBLEPRECISION, COMPLEX, or CHARACTER.

RETURNS

tostring

string representing all the input values

EXAMPLES

   Sample program:

      program demo_tostring
      use M_tostring, only : tostring
      implicit none
      character(len=:),allocatable :: pr

      pr=tostring('HUGE(3f) integer',huge(0),'and real',huge(0.0),'and double',huge(0.0d0))
      write(*,'(a)')pr
      pr=tostring('real            :',huge(0.0),0.0,12345.6789,tiny(0.0) )
      write(*,'(a)')pr
      pr=tostring('doubleprecision :',huge(0.0d0),0.0d0,12345.6789d0,tiny(0.0d0) )
      write(*,'(a)')pr
      pr=tostring('complex         :',cmplx(huge(0.0),tiny(0.0)) )
      write(*,'(a)')pr

      end program demo_tostring

   Expected output:

      HUGE(3f) integer 2147483647 and real 3.40282347E+38 and double 1.7976931348623157E+308
      real            : 3.40282347E+38 0.00000000 12345.6787 1.17549435E-38
      doubleprecision : 1.7976931348623157E+308 0.0000000000000000 12345.678900000001 2.2250738585072014E-308
      complex         : (3.40282347E+38,1.17549435E-38)

module M_tostring
implicit none
private
public tostring
contains

function tostring(generic1, generic2, generic3, generic4, generic5, generic6, generic7, generic8, generic9)
implicit none

! convert up to nine scalar intrinsic values to a string

class(*),intent(in),optional  :: generic1 ,generic2 ,generic3 ,generic4, generic5
class(*),intent(in),optional  :: generic6 ,generic7 ,generic8 ,generic9
character(len=:), allocatable :: tostring
character(len=4096)        :: line
integer                    :: istart

   istart=1
   if(present(generic1))call print_generic(generic1)
   if(present(generic2))call print_generic(generic2)
   if(present(generic3))call print_generic(generic3)
   if(present(generic4))call print_generic(generic4)
   if(present(generic5))call print_generic(generic5)
   if(present(generic6))call print_generic(generic6)
   if(present(generic7))call print_generic(generic7)
   if(present(generic8))call print_generic(generic8)
   if(present(generic9))call print_generic(generic9)
   tostring=trim(line)
contains
!===================================================================================================================================
   subroutine print_generic(generic)
   use,intrinsic :: iso_fortran_env, only : int8, int16, int32, int64, real32, real64, real128
   class(*),intent(in),optional :: generic
      select type(generic)
       type is (integer(kind=int8));     write(line(istart:),'(i0)') generic
       type is (integer(kind=int16));    write(line(istart:),'(i0)') generic
       type is (integer(kind=int32));    write(line(istart:),'(i0)') generic
       type is (integer(kind=int64));    write(line(istart:),'(i0)') generic
       type is (real(kind=real32));      write(line(istart:),'(1pg0)') generic
       type is (real(kind=real64));      write(line(istart:),'(1pg0)') generic
       type is (real(kind=real128));     write(line(istart:),'(1pg0)') generic
       type is (logical);                write(line(istart:),'(1l)') generic
       type is (character(len=*));       write(line(istart:),'(a)') generic
       type is (complex);                write(line(istart:),'("(",1pg0,",",1pg0,")")') generic
      end select
      istart=len_trim(line)+2
   end subroutine print_generic
!===================================================================================================================================
end function tostring
!===================================================================================================================================
end module M_tostring
!===================================================================================================================================