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Task/Arrays/LFE/arrays.lfe

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+; Create a fixed-size array with entries 0-9 set to 'undefined'
+> (set a0 (: array new 10))
+#(array 10 0 undefined 10)
+> (: array size a0)
+10
+
+; Create an extendible array and set entry 17 to 'true',
+; causing the array to grow automatically
+> (set a1 (: array set 17 'true (: array new)))
+#(array
+  18
+  ...
+(: array size a1)
+18
+
+; Read back a stored value
+> (: array get 17 a1)
+true
+
+; Accessing an unset entry returns the default value
+> (: array get 3 a1)
+undefined
+
+; Accessing an entry beyond the last set entry also returns the
+; default value, if the array does not have fixed size
+> (: array get 18 a1)
+undefined
+
+; "sparse" functions ignore default-valued entries
+> (set a2 (: array set 4 'false a1))
+#(array
+  18
+  ...
+> (: array sparse_to_orddict a2)
+(#(4 false) #(17 true))
+
+; An extendible array can be made fixed-size later
+> (set a3 (: array fix a2))
+#(array
+  18
+  ...
+
+; A fixed-size array does not grow automatically and does not
+; allow accesses beyond the last set entry
+> (: array set 18 'true a3)
+exception error: badarg
+  in (array set 3)
+
+> (: array get 18 a3)
+exception error: badarg
+  in (array get 2)