5.4 Cache Table
This module provides a set of caching hash table
functions.
Constructs a cache-table.
| (cache-table-lookup! ct id mk) → any/c | 
| ct : cache-table? | 
| id : symbol? | 
| mk : (-> any/c) | 
Looks up id in ct. If it is not present, then mk is
called to construct the value and add it to ct.
| (cache-table-clear! ct) → void? | 
| ct : cache-table? | 
Clears all entries in ct.
| (cache-table? v) → boolean? | 
| v : any/c | 
Determines if v is a cache table.