Stream pattern matcher

[Rene]

Here is a simple device that can detect a pattern in a stream of crates/barrels:

sutitud

The top device detects a pattern of 3 consecutive crates followed by a crate with two spaces inbetween. The bottom device detects a 1-2-1 pattern.
The pattern matcher only detects the presence of crates, not the absence. That is, the matcher will still trigger if there are crates in the gaps.
It does detect overlapping patterns correctly.

To see it in action in a solution, have a look at: kixuzuc (solution to livadul)