Creates an item stream of untyped data. Each item may be a Lisp object or an item stream.

  items implements the following option value pairs. These pairs are available in all item stream macros:

in {pattern}

Sets the pattern type of the stream, which defaults to cycle. Other available patterns are: accumulation, function, graph, heap, palindrome, random, rewrite, rotation and sequence.

for {integer | stream}

Sets the period length of the stream, which defaults to a pattern specific length. The value may be any non-negative number, including 0 or an item stream. If a period length is 0, then the stream is be omitted from the superior pattern until it is reselected and sets its period length to a number greater than 0. The period length counts subperiods or values in the pattern's data, depending on the value of the counting option.

counting {periods | values}

Controls whether the period length of the stream counts periods in the pattern or values returned in the pattern. If periods (the default), the number of items returned in the period is the sum of that many period lengths in the data. If values, the number of items returned is the same as the period length.

traversing {depth | breadth}

Controls whether the pattern visits its items in depth-first or breadth-first order. If depth (the default), the pattern increments only when the current item is at end-of-period. If breadth, the pattern increments each enumeration. (Traversing breadth may be implemented by setting the period lengths of all substreams to 1, but this is less efficient).

named {name}

Sets the name of the item stream. A named item stream may be subsequently referenced using find-item-stream, #@ or motive.

Example:

? (setf x (items 1 two 3 four in heap))
#<HEAP-ITEM-STREAM 133137601>

? (read-items x)
(3 FOUR 1 TWO)

See Also: