# 3 Backwards Compatibility

The modules described in this chapter provide functionality to increase interoperability with or upgrade from previous releases of Mozart.

## 3.1 The `TextPickle` module

The `TextPickle` module allows one to read text pickles written by Mozart 1.0.1. It may be imported as follows:

> `import TextPickle at 'x-oz://contrib/compat/TextPickle.ozf'`

`TextPickle.load`

  > `{TextPickle.load` `+V``` `X``` `?YTs``}`

  takes the name of a file `V` containing a text pickle and parses it. Returns the value represented by the pickle in `X`. `X` may have holes (unbound variables) in place of the data structures that could not be converted (at the moment, these include procedures and extensions except byte strings). `YTs` maps these holes to low-level descriptions of the corresponding data structures as described by the pickle; for procedures, this includes the instructions making up the body.