Function: COMMON-LISP:MAKE-HASH-TABLE

Create and return a new hash table. The keywords are as follows:

:TEST Determines how keys are compared. Must a designator for one of the standard hash table tests, or a hash table test defined using SB-EXT:DEFINE-HASH-TABLE-TEST. Additionally, when an explicit HASH-FUNCTION is provided (see below), any two argument equivalence predicate can be used as the TEST.

:SIZE A hint as to how many elements will be put in this hash table.

:REHASH-SIZE Indicates how to expand the table when it fills up. If an integer, add space for that many elements. If a floating point number (which must be greater than 1.0), multiply the size by that amount.

:REHASH-THRESHOLD Indicates how dense the table can become before forcing a rehash. Can be any positive number <=1, with density approaching zero as the threshold approaches 0. Density 1 means an average of one entry per bucket.

:HASH-FUNCTION If NIL (the default), a hash function based on the TEST argument is used, which then must be one of the standardized hash table test functions, or one for which a default hash function has been defined using SB-EXT:DEFINE-HASH-TABLE-TEST. If HASH-FUNCTION is specified, the TEST argument can be any two argument predicate consistent with it. The HASH-FUNCTION is expected to return a non-negative fixnum hash code.

:WEAKNESS When :WEAKNESS is not NIL, garbage collection may remove entries from the hash table. The value of :WEAKNESS specifies how the presence of a key or value in the hash table preserves their entries from garbage collection.

Valid values are:

:KEY means that the key of an entry must be live to guarantee that the entry is preserved.

:VALUE means that the value of an entry must be live to guarantee that the entry is preserved.

:KEY-AND-VALUE means that both the key and the value must be live to guarantee that the entry is preserved.

:KEY-OR-VALUE means that either the key or the value must be live to guarantee that the entry is preserved.

NIL (the default) means that entries are always preserved.

:SYNCHRONIZED If NIL (the default), the hash-table may have multiple concurrent readers, but results are undefined if a thread writes to the hash-table concurrently with another reader or writer. If T, all concurrent accesses are safe, but note that CLHS 3.6 (Traversal Rules and Side Effects) remains in force. See also: SB-EXT:WITH-LOCKED-HASH-TABLE. This keyword argument is experimental, and may change incompatibly or be removed in the future.

Lambda list

(&key sb-impl::test sb-impl::size sb-impl::rehash-size sb-impl::rehash-threshold
 sb-impl::hash-function sb-impl::weakness sb-impl::synchronized)