subroutine compact_real_string(str)

    implicit none

    character(kind=CK,len=*),intent(inout) :: str  !! string representation of a real number.

    character(kind=CK,len=len(str)) :: significand
    character(kind=CK,len=len(str)) :: expnt
    character(kind=CK,len=2) :: separator
    integer(IK) :: exp_start
    integer(IK) :: decimal_pos
    integer(IK) :: sig_trim
    integer(IK) :: exp_trim
    integer(IK) :: i  !! counter

    str = adjustl(str)
    exp_start = scan(str,CK_'eEdD')
    if (exp_start == 0) exp_start = scan(str,CK_'-+',back=.true.)
    decimal_pos = scan(str,CK_'.')
    if (exp_start /= 0) separator = str(exp_start:exp_start)

    if ( exp_start < decimal_pos ) then !possibly signed, exponent-less float

        significand = str
        sig_trim = len(trim(significand))
        do i = len(trim(significand)),decimal_pos+2,-1 !look from right to left at 0s
                                                       !but save one after the decimal place
            if (significand(i:i) == '0') then
                sig_trim = i-1
            else
                exit
            end if
        end do
        str = trim(significand(1:sig_trim))

    else if (exp_start > decimal_pos) then !float has exponent

        significand = str(1:exp_start-1)
        sig_trim = len(trim(significand))
        do i = len(trim(significand)),decimal_pos+2,-1 !look from right to left at 0s
            if (significand(i:i) == '0') then
                sig_trim = i-1
            else
                exit
            end if
        end do
        expnt = adjustl(str(exp_start+1:))
        if (expnt(1:1) == '+' .or. expnt(1:1) == '-') then
            separator = trim(adjustl(separator))//expnt(1:1)
            exp_start = exp_start + 1
            expnt     = adjustl(str(exp_start+1:))
        end if
        exp_trim = 1
        do i = 1,(len(trim(expnt))-1) !look at exponent leading zeros saving last
            if (expnt(i:i) == '0') then
                exp_trim = i+1
            else
                exit
            end if
        end do
        str = trim(adjustl(significand(1:sig_trim)))// &
              trim(adjustl(separator))// &
              trim(adjustl(expnt(exp_trim:)))

    !else ! mal-formed real, BUT this code should be unreachable

    end if

    end subroutine compact_real_string