le book-adaptive classifier for various character sets,
   segmentation for newspaper articles, etc.

13. Data structures

   Several simple data structures are provided for safe and efficient handling
   of arrays of numbers, strings, pointers, and bytes.  The generic
   pointer array is implemented in four ways: as a stack, a queue,
   a heap (used to implement a priority queue), and an array with
   insertion and deletion, from which the stack operations form a subset.
   Byte arrays are implemented both