Concept:HashTable

Hash tables can be seen in many implementations, with the following variations.

• Compare function : fixed or user-customizable
• Hash function : fixed or user-customizable
• External representation
• API

R6RS

• Compare and hash: User-customizable by make-hashtable. The fixed ones are also provided by make-eq-hashtable and make-eqv-hashtable.
• External: no
• API: make-eq-hashtable, make-eqv-hashtable, make-hashtable, hashtable?, hashtable-size, hashtable-ref, hashtable-set!, hashtable-delete!, hashtable-contains?, hashtable-update!, hashtable-copy, hashtable-clear!, hashtable-keys, hashtable-entries, hashtable-equivalence-function, hashtable-hash-function, hashtable-mutable?, equal-hash, string-hash, string-ci-hash, symbol-hash

Bigloo

• Compare : (fixed?)
• Hash : (fixed?)
• External : no
• API : make-hashtable, hashtable?, hashtable-size, hashtable-get, hashtable-put!, hashtable-remove!, hashtable-update!, hashtable->vector, hashtable->list, hashtable-for-each?, object-hashnumber?

Chicken

• Compare : user-specified (default eq?)
• Hash : fixed (makes some comparators like string-ci=? useless)
• External : No
• API : clear-hash-table!, get, hash-table?, hash-table-count, hash-table-for-each, hash-table-ref, hash-table-set!, make-hash-table, put!, hash-table-size

Gauche

• Compare : eq?, eqv?, equal?, string=?; user-defined object can have its own equality function via object-equal?? method.
• Hash : user-defined object can have its own hash function via object-hash method.
• External : No
• API : make-hash-table, hash-table-get, hash-table-put!, hash-table-delete!, hash-table-clear!, hash-table-update!, hash-table-push!, hash-table-pop!, hash-table-exists?, hash-table?, hash-table-map, hash-table-for-each, hash-table-keys, hash-table-values

MIT-Scheme

• Compare : user specified
• Hash : user specified
• External : ?
• API : make-eq-hash-table?, make-eqv-hash-table?, make-equal-hash-table?, make-string-hash-table?, strong-hash-table-constructor?, weak-hash-table-constructor?, hash-table?, hash-table/put!?, hash-table/get?, hash-table/remove!?, hash-table/clear!?, hash-table/count?, hash-table->alist, hash-table/key-list?, hash-table/datum-list?, hash-table/for-each?, hash-table/lookup?

MzScheme

• Compare : eq? or equal?
• Hash : fixed
• External : Yes
• API : make-hash-table, make-hash-table-weak, hash-table?, hash-table-put!, hash-table-get, hash-table-remove!, hash-table-map, hash-table-for-each

Scheme48

• Compare : eq?, eqv?, string=?, =, or user-specified
• Hash : system default or user specified.
• External : No
• API : make-table, make-symbol-table, make-string-table, make-integer-table, make-table-maker, make-table-immutable!, table?, table-ref, table-set!, table-walk, default-hash-function, string-hash

STk

• Compare : user specified (default eq?)
• Hash : user specified (default hash-table-hash).
• API : make-hash-table, hash-table?, hash-table-put!, hash-table-hash, hash-table-get, hash-table-remove!, hash-table-for-each, hash-table-map, hash-table->list, hash-table-stats.

SRFI-69

• Compare : user-specified (default equal?)
• Hash : user-specified (defaults to an appropriate hash function for the given compare function)
• External : No
• API : See SRFI-69 code rio