.. efun:: string save_value(mixed value)
  string save_value(mixed value, int format)

  Encode the :arg:`value` into a string suitable for restoration with :efun:`restore_value` and return it.

  The optional :arg:`format` argument determines the format of the savefile to be written:

     -1: use the driver's native format (default).
      0: original format, used by Amylaar LPMud and LDMud <= 3.2.8 .
      1: LDMud >= 3.2.9: no-lambda closures, symbols, quoted arrays can be saved.
      2: LDMUd >= 3.5.0: floats are stored in a different way, which is more compact and can store the new floats losslessly.

  .. todo:: revise above

  It is recommended to use version 2 or higher.

  .. todo:: should above be a table?

  The created string consists of two lines, each terminated with a newline character: the first line describes the format used to save the value in the ``#x:y`` notation; the second line is the representation of the value itself.

  The format of the encoded value and of the format line matches the format used by :efun:`save_object` and :efun:`restore_object`.

  .. todo:: see re: question about where to document these formats

  :history 3.2.8 introduced:
  :history 3.2.9 changed: added restoring of non-lambda closures, symbols, and quoted arrays, using a new savefile format version 1.
  :history 3.2.10 changed: added the :arg:`format` argument.
  :history 3.5.0 changed: added the possibility to restore version 2 with its higher float precision.

  .. seealso:: :efun:`restore_value`, :efun:`restore_object`, :efun:`save_object`