![[XANALYS]](../Graphics/XanSmall.gif)
Syntax:
maphash function hash-table => nil
Arguments and Values:
function---a designator for a function of two arguments, the key and the value.
hash-table---a hash table.
Description:
Iterates over all entries in the hash-table. For each entry, the function is called with two arguments--the key and the value of that entry.
The consequences are unspecified if any attempt is made to add or remove an entry from the hash-table while a maphash is in progress, with two exceptions: the function can use can use setf of gethash to change the value part of the entry currently being processed, or it can use remhash to remove that entry.
Examples:
(setq table (make-hash-table)) => #<HASH-TABLE EQL 0/120 32304110>
(dotimes (i 10) (setf (gethash i table) i)) => NIL
(let ((sum-of-squares 0))
(maphash #'(lambda (key val)
(let ((square (* val val)))
(incf sum-of-squares square)
(setf (gethash key table) square)))
table)
sum-of-squares) => 285
(hash-table-count table) => 10
(maphash #'(lambda (key val)
(when (oddp val) (remhash key table)))
table) => NIL
(hash-table-count table) => 5
(maphash #'(lambda (k v) (print (list k v))) table)
(0 0)
(8 64)
(2 4)
(6 36)
(4 16)
=> NIL
Side Effects:
None, other than any which might be done by the function.
Affected By: None.
Exceptional Situations: None.
See Also:
loop, with-hash-table-iterator, Section 3.6 (Traversal Rules and Side Effects)
Notes: None.