srfi-69 | chickadee

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Outdated CHICKEN release
Unit srfi-69

Unit srfi-69

CHICKEN implements SRFI 69 with SRFI 90 extensions. For more information, see SRFI-69 and SRFI-90.

Hash Table Procedures

make-hash-table

(make-hash-table [TEST HASH SIZE] [#:test TEST] [#:hash HASH] [#:size SIZE] [#:initial INITIAL] [#:min-load MIN-LOAD] [#:max-load MAX-LOAD] [#:weak-keys WEAK-KEYS] [#:weak-values WEAK-VALUES])procedure

Returns a new HASH-TABLE with the supplied configuration.

TEST: The equivalence function.
HASH: The hash function.
SIZE: The expected number of table elements.
INITIAL: The default initial value.
MIN-LOAD: The minimum load factor. A flonum in (0.0 1.0).
MAX-LOAD: The maximum load factor. A flonum in (0.0 1.0).
WEAK-KEYS: Use weak references for keys. (Ignored)
WEAK-VALUES: Use weak references for values. (Ignored)

Please note that hash tables are not guaranteed to compare equal? to each other, even if they contain exactly the same key/value pairs.

alist->hash-table

(alist->hash-table A-LIST [#:test TEST] [#:hash HASH] [#:size SIZE] [#:initial INITIAL] [#:min-load MIN-LOAD] [#:max-load MAX-LOAD] [#:weak-keys WEAK-KEYS] [#:weak-values WEAK-VALUES])procedure

Returns a new HASH-TABLE. The HASH-TABLE is populated from the A-LIST. The keyword arguments are per make-hash-table.

If a key occurs multiple times in A-LIST, the first occurrence will be used in the hash table.

hash-table?

hash-table? OBJECTprocedure: Is the OBJECT a hash-table?

hash-table-size

hash-table-size HASH-TABLEprocedure: Returns the number of associations in HASH-TABLE.

hash-table-equivalence-function

hash-table-equivalence-function HASH-TABLEprocedure: The HASH-TABLE equivalence-function.

hash-table-hash-function

hash-table-hash-function HASH-TABLEprocedure: The HASH-TABLE hash-function.

hash-table-min-load

hash-table-min-load HASH-TABLEprocedure: The HASH-TABLE minimum load factor.

hash-table-max-load

hash-table-max-load HASH-TABLEprocedure: The HASH-TABLE maximum load factor.

hash-table-weak-keys

hash-table-weak-keys HASH-TABLEprocedure: Does the HASH-TABLE use weak references for keys?

hash-table-weak-values

hash-table-weak-values HASH-TABLEprocedure: Does the HASH-TABLE use weak references for values?

hash-table-has-initial?

hash-table-has-initial? HASH-TABLEprocedure: Does the HASH-TABLE have a default initial value?

hash-table-initial

hash-table-initial HASH-TABLEprocedure: The HASH-TABLE default initial value.

hash-table-keys

hash-table-keys HASH-TABLEprocedure: Returns a list of the keys in the HASH-TABLE population.

hash-table-values

hash-table-values HASH-TABLEprocedure: Returns a list of the values in the HASH-TABLE population.

hash-table->alist

hash-table->alist HASH-TABLEprocedure: Returns the population of the HASH-TABLE as an a-list.

hash-table-ref

hash-table-ref HASH-TABLE KEYprocedure

Returns the VALUE for the KEY in the HASH-TABLE.

Aborts with an exception when the KEY is missing.

hash-table-ref/default

hash-table-ref/default HASH-TABLE KEY DEFAULTprocedure: Returns the VALUE for the KEY in the HASH-TABLE, or the DEFAULT when the KEY is missing.

hash-table-exists?

hash-table-exists? HASH-TABLE KEYprocedure: Does the KEY exist in the HASH-TABLE?

hash-table-set!

hash-table-set! HASH-TABLE KEY VALUEprocedure

Set the VALUE for the KEY in the HASH-TABLE.

A setter for hash-table-ref is defined, so

(set! (hash-table-ref HASH-TABLE KEY) VALUE)

is equivalent to

(hash-table-set! HASH-TABLE KEY VALUE)

hash-table-update!

hash-table-update! HASH-TABLE KEY #!optional UPDATE-FUNCTION DEFAULT-VALUE-FUNCTIONprocedure

Sets or replaces the VALUE for KEY in the HASH-TABLE.

The UPDATE-FUNCTION takes the existing VALUE for KEY and returns the new VALUE. The default is identity

The DEFAULT-VALUE-FUNCTION is called when the entry for KEY is missing. The default uses the (hash-table-initial-value), if provided. Otherwise aborts with an exception.

Returns the new VALUE.

hash-table-update!/default

hash-table-update!/default HASH-TABLE KEY UPDATE-FUNCTION DEFAULT-VALUEprocedure

Sets or replaces the VALUE for KEY in the HASH-TABLE.

The UPDATE-FUNCTION takes the existing VALUE for KEY and returns the new VALUE.

The DEFAULT-VALUE is used when the entry for KEY is missing.

Returns the new VALUE.

hash-table-copy

hash-table-copy HASH-TABLEprocedure: Returns a shallow copy of the HASH-TABLE.

hash-table-delete!

hash-table-delete! HASH-TABLE KEYprocedure: Deletes the entry for KEY in the HASH-TABLE.

hash-table-remove!

hash-table-remove! HASH-TABLE PROCprocedure: Calls PROC for all entries in HASH-TABLE with the key and value of each entry. If PROC returns true, then that entry is removed.

hash-table-clear!

hash-table-clear! HASH-TABLEprocedure: Deletes all entries in HASH-TABLE.

hash-table-merge

hash-table-merge HASH-TABLE-1 HASH-TABLE-2procedure: Returns a new HASH-TABLE with the union of HASH-TABLE-1 and HASH-TABLE-2. Keys that exist in both tables will be taken from HASH-TABLE-1.

hash-table-merge!

hash-table-merge! HASH-TABLE-1 HASH-TABLE-2procedure: Returns HASH-TABLE-1 as the union of HASH-TABLE-1 and HASH-TABLE-2. Keys that exist in both tables will be taken from HASH-TABLE-1.

hash-table-map

hash-table-map HASH-TABLE FUNCprocedure

Calls FUNC for all entries in HASH-TABLE with the key and value of each entry.

Returns a list of the results of each call.

hash-table-fold

hash-table-fold HASH-TABLE FUNC INITprocedure

Calls FUNC for all entries in HASH-TABLE with the key and value of each entry, and the current folded value. The initial folded value is INIT.

Returns the final folded value.

hash-table-for-each

hash-table-for-each HASH-TABLE PROCprocedure: Calls PROC for all entries in HASH-TABLE with the key and value of each entry.

hash-table-walk

hash-table-walk HASH-TABLE PROCprocedure: Calls PROC for all entries in HASH-TABLE with the key and value of each entry.

Hashing Functions

All hash functions return a fixnum in the range [0 BOUND).

When given the fixnum RANDOMIZATION, these functions will use this to perturb the value; if not specified, the value will differ for each invocation of your program. This is for security reasons; an attacker who knows what a value hashes to can deliberately try to cause collisions, thereby flattening your hash table, effectively reducing it to a list. Always make sure you don't expose any hashed value to an attacker.

string-hash

(string-hash STRING [BOUND START END RANDOMIZATION])procedure: For use with string=? as a hash-table-equivalence-function. The optional START and END arguments may be given to limit the hash calculation to a specific sub-section of STRING.