Programmable Water (2003) | Hacker News Reader

Programmable Water (2003)

blikstein.com

87 pointsllambda19 comments

The air version, Pneumatic logic:

http://en.wikipedia.org/wiki/Pneumatics#Pneumatic_logic

it's taken me a good 5 minutes to convince myself a single device can be both AND and XOR. that's weird stuff.

is there any way to get AND, XOR and NOR in a single device "for free"? after all, they don't overlap (only one is 1 for any given pair of inputs).

also, how do you build a practical system when the flow rate is not constant (AND doubles the flow here, for example)?

>also, how do you build a practical system when the flow rate is not constant (AND doubles the flow here, for example)?

You could probably make it constant. In this case, at the output of the AND gate, put a pressure regulator valve, that will allow the extra pressure to leak out of the system (or into a return pipe).

A similar problem would be duplicating the signal. The simplest solution I can see is a device that has two always pressurized inputs, and one control input. When the control is pressurized, it leverages a spring loaded switch to allow the two always on streams through.

That is a transistor.

a single device can be both AND and XOR. that's weird stuff.

I'd say it depends on how you would define "single device". Imagine the possible complexity of such water devices build with a 3D printer and still it's just a lump of uniform material, albeit structured.

I think that a distinction can be made here. Consider the device as an XOR gate. There is no element within the device that is not a fundamental part of the XOR system. The AND gate arises as a natural result of constructing the XOR gate. This feels fundamentally different from constructing an XOR gate, and then adding an AND gate.

On a meta-level, in writing the above comment, I feel as if we are missing some critical vocabulary that would make this entire question seem trivial. Any ideas on what this vocab. is?

If you combined the output hoses you'd get an OR. So you have AND, OR, and XOR in one device. You can make a NOT from the same device using the XOR and connecting an input to the water source.

It can be both AND and XOR because it has two outputs. You could add a 3rd output for NOR in theory. You would probably add a 3rd always-on stream that drains into the NOR output by default but is deflected away when either or both of the other streams comes through.

I guess this adds a whole new meaning to the phrase "bit bucket" :).

bro, do you even CSS?

How does this story get 56 points and frontpage (as of this writing), yet when I submitted an article on computing with water droplets on superhydrophobic surfaces [1], it didn't get any upvotes at all?

Anyone have ideas for reducing the tendency of HN to sometimes ignore high-quality content? I shudder to think about how stressful being ignored must be for startups who try to launch their product or get feedback here...

EDIT: Multiple downvotes? Does this mean that people are uncomfortable with the idea that HN may be less than perfect? Or is it merely because my comment's too far off-topic?

[1] https://news.ycombinator.com/item?id=4885419

Don't take it personally dude. It's a human system, therefore an inherently flawed one.

I'm not taking it personally. I'm trying to ask all the clever people here to put their hacking hats on, and think up an analysis of this particular flaw, or ideas for technological ways to mitigate this problem.

I am a little bitter about the situation, I suppose, and maybe this leaked into my comment. My intention was to set the tone of a matter between adult professionals: "Here's a problem I experienced. Let's try to solve it." Maybe I didn't entirely succeed in setting that tone.

For the least common denominator of HN visitors a title like "programmable water" is more attractive than what you proposed.

This is a problem that won't be solved with an algorithm. Emotions dictate the actions of humans. It's hard to fix that problem.

You sound like someone who checks your watch to figure out whether you're hungry or not.

Multiple downvotes are because your comment adds nothing to the conversation of this article, and most likely people are tired of hearing about somebody's submission not getting the love they think it deserves, and now you'll probably get even more for looking like you care about your score.

And yes, I'm aware that I'm not contributing to the discussion about the article myself.

you post things because _you_ found them interesting, not so as to get upvotes. any upvotes gathered are purely incidental...

I'd contend that while upvotes are purely incidental, comments and discussion are reasons to post something.

I suggest you read this essay from pg [1]. Getting a link to HN front page is very similar to most things in life. Luck plays a big role. I recommend that essay and urge you to realize, your (and my) inputs to HN are like that 20th best player for the 20 person team.

It is not important for HN to pick up (reward) every great link posted; it is only important that all links that make front page are quality.

1: http://www.paulgraham.com/judgement.html

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