Module window

source code

window PREDICATE

window -o WINDOW_SIZE

window -d WINDOW_SIZE

Groups of consecutive input objects are formed into tuples which are passed to the output stream. The objects are grouped in one of two mechanisms.

1) A new group is started on the first input object, and for any subsequent object for which PREDICATE returns true. For example, if the input stream contains the integers 1, 2, 3, ..., then:

   window 'n: n % 3 == 2'

yields as output:

   ((1,),)
   ((2,), (3,), (4,))
   ((5,), (6,), (7,))
   ((8,), (9,), (10,))
   ...

I.e., a new tuple is started for each integer n such that n % 3 = 2.

2) Groups have a fixed number of objects. The -o and -d flags specify WINDOW_SIZE, the number of objects in the groups. -o specifies overlapping windows, in which each input object begins a new list containing WINDOW_SIZE items. Groups may be padded with None values to ensure that the group's size is WINDOW_SIZE.

Example: For input 0, 1, ..., 9, window -o 3 yields these tuples:

   ((0,), (1,), (2,))
   ((1,), (2,), (3,))
   ((2,), (3,), (4,))
   ((3,), (4,), (5,))
   ((4,), (5,), (6,))
   ((5,), (6,), (7,))
   ((6,), (7,), (8,))
   ((7,), (8,), (9,))
   ((8,), (9,), (None,))
   ((9,), (None,), (None,))

-d specifies disjoint windows, in which each input object appears in only one group. A new group is started every WINDOW_SIZE objects. The last window may be padded with (None,) to ensure that it has WINDOW_SIZE elements.

Example: For input 0, 1, ..., 9, window -d 3 yields these tuples:

   ((0,), (1,), (2,))
   ((3,), (4,), (5,))
   ((6,), (7,), (8,))
   ((9,), (None,), (None,))