Keyword :test can be `eq', `eql' (default) or `equal'.
Comparison between keys is done using this function.
If speed is important, consider using `eq'.
-When storing strings in the hash table, you will likely need to use `equal'.
+When hash table keys may be strings, you will likely need to use `equal'.
Keyword :size specifies the number of keys likely to be inserted.
This number of entries can be inserted without enlarging the hash table.