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ANSI Common Lisp  18 Hash Tables 18.2 Dictionary of Hash Tables
- 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.
- See Also:
-
loop,
with-hash-table-iterator,
Section 3.6 Traversal Rules and Side Effects
- Allegro CL Implementation Details:
-
None.
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