Reaction types and terminology

[tod222]

[Edited Dec. 22 for spark reaction.]

I was wondering about the terminology used for different types of reactions between an active region and a still life. It seems that there are two axes, each with two possibilities:

Code: Select all

+---------------+---------------+--------------------+
|   Modifies    |     Object    |       Object       |
|    Result     |    Consumed   |     Re-created     |
+---------------+---------------+--------------------+
|  Yes          |   1. Normal   |   2. Transparent   |
+---------------+---------------+--------------------+
|  No           |   3. Spark    |   4. Redundant     |
+---------------+---------------+--------------------+

(Pardon the ASCII art -- HTML tables aren't available.)

1. Normal. The usual reaction where the object is consumed, modifying the reaction in the process.
2. Transparent. From LifeWiki: A transparent debris effect is a reaction in which a Herschel or other active region destroys a still life, then later, having passed through the place where the still life was, recreates the still life in its original position. Nothing is said about modifying the reaction. But both the canonical example of the transparent block reaction with the B-heptomino and the notable example of the beehive in the Rectifier involve the object modifying the reaction.
3. Spark. An optionally-appearing object is consumed without getting re-created. When present, the object's consumption has no effect on the reaction. Canonical examples are the many spark reactions capable of deleting an optionally-appearing object.
4. Redundant. An object is created in the location whether or not one existed beforehand.

Are these reaction types discussed anywhere? Is there a name for type 4? If not, I nominate redundant reaction for type 4.

What about canonical examples? I can't think of any examples offhand, but I don't think type 3s are that rare.

For type 4 I'm aware of knightlife's pattern discussed in his topic Overwrite a Block. Is there a more notable example?

This is all in the context of finding test cases for my pattern evaluator which does before-and-after comparisons of small patterns.

[Axaj]

Well, I don't think this has really been brought up before (at least in the amateur sphere). I'm personally fine with those names, but I'm sure someone will want to have something else.

[calcyman]

Is there a more notable example?

Yes, the block keeper and blinker keeper reactions fall into this category. There are several examples of each, and even a variable-period gun based on the blinker keeper.

but I don't think type 3s are that rare.

What about every reaction that throws off sparks, capable of deleting nearby objects? Are they type-3?

[Axaj]

but I don't think type 3s are that rare.

What about every reaction that throws off sparks, capable of deleting nearby objects? Are they type-3?

I think so. This definition should include that.

[tod222]

Yes, the block keeper and blinker keeper reactions fall into this category. There are several examples of each, and even a variable-period gun based on the blinker keeper.

Ahh, thanks. I found the writeup on the blinker keeper, but nothing about the block keeper.

What about every reaction that throws off sparks, capable of deleting nearby objects? Are they type-3?

Yes. I've edited my original post to indicate that type 3s should be termed the Spark reaction, since that name is so familiar. They're also common -- I wrote a script which found 165 locations where blocks can be consumed by an evolving r-pentomino without modifying the result. Most are clustered around the edges of the reaction history.