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Associative array/Iteration: Difference between revisions
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Values: Netherlands, USA, Netherlands
Unique values: Netherlands, USA
</pre>
=={{header|Scheme}}==
{{works with|Gauche Scheme}}
<lang Scheme>
;; Create an associative array (hash-table) whose keys are strings:
(define table (hash-table 'string=?
'("hello" . 0) '("world" . 22) '("!" . 999)))
;; Iterate over the table, passing the key and the value of each entry
;; as arguments to a function:
(hash-table-for-each
table
;; Create by "partial application" a function that accepts 2 arguments,
;; the key and the value:
(pa$ format #t "Key = ~a, Value = ~a\n"))</lang>
Output:
<pre>
Key = !, Value = 999
Key = world, Value = 22
Key = hello, Value = 0
</pre>
<lang Scheme>
;; Iterate over the table and create a list of the keys and the
;; altered values:
(hash-table-map
table
(lambda (key val) (list key (+ val 5000))))
;; Create a new table that has the same keys but altered values.
(use gauche.collection)
(map-to <hash-table>
(lambda (k-v) (cons (car k-v) (+ (cdr k-v) 5000)))
table)
</lang>
To get a list of the keys or of the values of the table,
use one of the following:
<pre>
(hash-table-keys table)
(hash-table-values table)
</pre>
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