tokenize Subroutine

  pure subroutine tokenize(strin, delimiter, toks, Nt)
  !< Tokenize a string in order to parse it.
  !<
  !< @note The dummy array containing tokens must allocatable and its character elements must have the same length of the input
  !< string. If the length of the delimiter is higher than the input string one then the output tokens array is allocated with
  !< only one element set to input string.
  character(len=*),          intent(in)               :: strin     !< String to be tokenized.
  character(len=*),          intent(in)               :: delimiter !< Delimiter of tokens.
  character(len=len(strin)), intent(out), allocatable :: toks(:)   !< Tokens.
  integer(I4P),              intent(out), optional    :: Nt        !< Number of tokens.
  character(len=len(strin))                           :: strsub    !< Temporary string.
  integer(I4P)                                        :: dlen      !< Delimiter length.
  integer(I4P)                                        :: c         !< Counter.
  integer(I4P)                                        :: n         !< Counter.
  integer(I4P)                                        :: t         !< Counter.

  ! initialization
  if (allocated(toks)) deallocate(toks)
  strsub = strin
  dlen = len(delimiter)
  if (dlen>len(strin)) then
    allocate(toks(1:1)) ; toks(1) = strin ; if (present(Nt)) Nt = 1 ; return
  endif
  ! compute the number of tokens
  n = 1
  do c=1,len(strsub)-dlen ! loop over string characters
    if (strsub(c:c+dlen-1)==delimiter) n = n + 1
  enddo
  allocate(toks(1:n))
  ! tokenization
  do t=1,n ! loop over tokens
    c = index(strsub, delimiter)
    if (c>0) then
      toks(t) = strsub(1:c-1)
      strsub = strsub(c+dlen:)
    else
      toks(t) = strsub
    endif
  enddo
  if (present(Nt)) Nt = n
  endsubroutine tokenize