tostring in Fortran Wiki

## 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)
~~~~~~~~~~ {: lang=fortran}
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
!===================================================================================================================================
~~~~~~~~~~
category: code