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Comment by acqq | Hacker News Reader

A typical example that just appears to be "insightful" while what is happening in the actual logic gates has no similarity with that at all:

https://www.youtube.com/watch?v=58nSgVvXVbo

so any "intuition" one might hope to gain from these two pipes will be wrong.

Therefore "explain logic gates" is an incorrect title. It can be used to explain the truth table for AND, but not the gates.

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“Logic gate” can (and does) refer to the idealized concept, and is already disctinctly different from the implementation, e.g., an electronic logic circuit. Gates can be implemented with relays, physical switches or water.

https://en.m.wikipedia.org/wiki/Logic_gate

Why wouldn’t the intuition here be helpful? You can, in fact, build an actual computer out of water based logic gates.

"Logic gates" is an abstract concept, and yes, it is essentially a truth table.

You refer to one of the transistor-based implementations of logic gates. Yes, it works differently.

I refer to any kind of logic gates actually used in the devices we use -- otherwise what is there to "explain"?

The boolean algebra part.

For "the boolean algebra part" the table like from here (second slide) is a real explanation:

https://courses.cs.washington.edu/courses/cse370/03au/lectur...

"There are 16 possible functions of 2 input variables: in general, there are 2^(2^n) functions of n inputs"

"And" from the original tweet is just one of them.

You can build logic gates out of just about anything.

One of my favorites is the Digi-Comp II, which uses (in this modern version) laser cut wood, steel balls, and gravity:

https://www.evilmadscientist.com/2012/dcii-first/

There can be real value in explaining logic gates using things you can see and touch and observe in action.

> You can build logic gates out of just about anything.

Does that fact (which I never denied) in any way provide the original "pipes" picture any explanatory power, helping somebody to more understand the how the logic gates actually used in our devices function?

I still don't see that any answer here up to now disproved my original claim: "what is happening in the actual logic gates [meaning the gates that are actually used in our devices] has no similarity with that [the pipes thing] at all -- so any "intuition" one might hope to gain from these two pipes will be wrong."

I still claim that.

The "pipes" don't "explain" anything but demonstrate their own functioning.

TTL or CMOS aspects are also not relevant for this discussion, contrary to what "neuralRiot" writes.

Also see what user "zemnmez" wrote here.

Friend, I'm not saying you were wrong or trying to argue with you. Just pointing out that different people learn differently, and it's good to have different ways to illustrate and explain things.

You never know when one kind of explanation may give someone an "aha" moment that they didn't get somewhere else. And sometimes it's good to do things like this just for fun.

For example, my very favorite visualizations of sorting algorithms are the Hungarian dancers:

https://www.youtube.com/watch?v=ywWBy6J5gz8

(Turn the sound up to enjoy the music!)

My intuitions about the world (and I guess most everyone's) roughly divide it into two kinds of things: agents and inanimate objects. It's most obvious and natural then to see a computer as a kind of agent, built out of smaller dumber sub-agents. (There have been psych studies showing young kids often include computers in the 'living things' bin, so I don't think this is just me here.) In the end with this intuition you get logic gates as particularly simpleminded agents.

Maybe this is just me, and it feels stupid to admit it, but I felt a definite shift of perspective on really seeing logic gates as inanimate. I had a related shift about F=ma around the same time, which is hard to articulate without sounding even stupider. You want to think of it like "you push, and the object accelerates" when from this nonanimate point of view there is no you causing things, there's only a network of constraints.

CMOS logic is actually really simple and easy to understand (from a functional model of ideal CMOS transistors). Indeed a water analogue shouldn't be necessary if one wants to understand modern gates themselves.

Which is not how actual gates work, if you’re gonna get nitpicky since most of of them are composed of CMOS transistors. You can see a “real” AND gate internal circuit here:http://www.ti.com/lit/ds/schs057c/schs057c.pdf

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