rgnwrd.gsf

function rgnwrd( str, n_start, n_end, sep )

*  If separator is space, just use subwrd() for output.
*  if( sep = 'sep' | sep = '' | sep = ' ' )
  if( sep = 'sep' | sep = '' )
    n = n_start
    ret = ''
    while( n <= n_end )
      tmp = subwrd( str, n )
      if( tmp = '' ) ; break ; endif
      ret = ret % tmp % ' '
      n = n + 1
    endwhile

  else
    ret = ''
    len_sep = math_strlen( sep )
    len     = math_strlen( str )
    p = 1
    i = 1
    imin = -1
    if( n_start = 1 ) ; imin = 1 ; endif
    imax = len
    while( i <= len )
      c = substr( str, i, len_sep )
      if( c = sep )
        p = p + 1
        if( p = n_start ) ; imin = i + len_sep ; endif
        if( p > n_end   ) ; imax = i - len_sep ; break ; endif
        i = i + len_sep
      else
        i = i + 1
      endif
    endwhile
    if( imin = -1 | imin > imax ) ; ret = ''
    else ; ret = substr( str, imin, imax-imin+1 ) ; endif

  endif
return ret