The library allows you to allocate memory in a region yielding a regional pointer to it. When the region terminates all pointers are automatically freed. Most importantly, a pointer can't be returned from the region. So it's impossible to reference unallocated memory. The primary technique used in this package is called "Lightweight monadic regions" which was invented by Oleg Kiselyov and Chung-chieh Shan. See: http://okmij.org/ftp/Haskell/regions.html#light-weight This technique is implemented in the regions package which is re-exported from this library. This library provides wrappers around all the Ptr functions from the Foreign.* modules from base.