program testIntToString
print *,('"',inttostring(i),'",',i=-100,100)
contains

function IntToString(i)   ! This version can be used in I/O statements
    implicit none
    integer :: i
! The following elaborate declaration is required to define a string
! having just enough positions to hold all the digits of the integer,
! and the sign character.
! It contains constants no greater than 10000, so as to be acceptable
! on machines having a default integer kind of 16 bits or more.
! (borrowed from "Algorithms and Data Structures in F and Fortran"
!  By Robin A. Vowels - Published by Unicomp, 1998. ISBN 0-9640135-4-1)
!   character (len = 1 +                             & ! For 1-digit
!       min (abs(i/10),                         1) + & ! For 2-digit->1
!       min (abs(i/100),                        1) + & ! For 3-digit->1
!       min (abs(i/1000),                       1) + & ! For 4-digit->1
!       min (abs(i/10000),                      1) + & ! For 5-digit->1
!       min (abs(i/10000)/10,                   1) + & ! For 6-digit->1
!       min (abs(i/10000)/100,                  1) + & ! For 7-digit->1
!       min (abs(i/10000)/1000,                 1) + & ! For 8-digit->1
!       min (abs(i/10000)/10000,                1) + & ! For 9-digit->1
!       min (abs(i/10000)/10000/10,             1) + & ! For 10 digits
!       min (abs(i/10000)/10000/100,            1) + & ! For 11 digits
!       min (abs(i/10000)/10000/1000,           1) + & ! For 12 digits
!       min (abs(i/10000)/10000/10000,          1) + & ! For 13 digits
!       min (abs(i/10000)/10000/10000/10,       1) + & ! For 14 digits
!       min (abs(i/10000)/10000/10000/100,      1) + & ! For 15 digits
!       min (abs(i/10000)/10000/10000/1000,     1) + & ! For 16 digits
!       min (abs(i/10000)/10000/10000/10000,    1) + & ! For 17 digits
!       min (abs(i/10000)/10000/10000/10000/10, 1) + & ! For 18 digits
!       min (abs(i/10000)/10000/10000/10000/100,1) - & ! For 19 digits
!       min (max(i, -1), 0)                          & ! For -ive nums
!              )       :: IntToString
    character( max(1, int(log10(real(abs(i))+0.1)) + (3-sign(1,i))/2) )&
            :: IntToString
    integer :: val , p , izero=iachar('0')

    if ( i<0 ) then
       IntToString(1:1) = '-'
    elseif ( i==0 ) then
       IntToString(1:1) = '0'
    endif
    val = abs(i)

    p = len(IntToString)
    do while( val>0 )
       IntToString(p:p) = achar(izero + mod(val,10))
       val = val/10
       p = p - 1
    end do
end function IntToString
end program testIntToString