hash-table-update!

[procedure] hash-table-update! hash-table key function [thunk]

SRFI-69: Semantically equivalent to, but may be implemented more efficiently than, the following code:

(hash-table-set! hash-table key
                 (function (hash-table-ref hash-table key thunk)))

[procedure] hash-table-update! hash key update-fun init-value

STklos: update the entry of hash table hash associated with key. See make-hash-table.

See also Concept:HashTable.

R6RS has hashtable-update!.