Pileup is a portable, performant, and thread-safe binary heap for Common
Lisp, under an MIT-style licence.

The rest of this file is best viewed under org-mode.

TODO for 2.0

* WIP HEAP-DELETE should accept keyword arguments similar to CL:DELETE.
*** TODO :TEST -- keep it performant, simplify EQL to inline EQ when possible.
*** TODO :KEY -- default to NIL or HEAP-KEY?
    If TEST or KEY is used, HEAP-DELETE needs to traverse the entire
    heap: it is not generally possible to know if (FUNCALL TEST ELT X)
    implies anything about the ordering, unlike with EQL.
* TODO MAKE-HEAP should also accept :ELEMENT-TYPE.
  Unboxed allocation for long-lived heaps storing numbers.
* TODO Add other types of heaps.