# The logic of lifts

#### Speakpigeon

Valued Senior Member
Can computer-literate people specify a lift, a usual lift, going up and down, stopping at floors etc. using only formal logic?
I'm interested in the principle, no need to get all fussy about it. The simpler the better.
No algorithm allowed. Only ordinary logic. Conjunctions and such, two truth values only, etc.
EB

Can computer-literate people specify a lift, a usual lift, going up and down, stopping at floors etc. using only formal logic?
I'm interested in the principle, no need to get all fussy about it. The simpler the better.
No algorithm allowed. Only ordinary logic. Conjunctions and such, two truth values only, etc.
EB
Tell you what: why don't you offer a way of doing it for once, to give us a chance to be the ones to take potshots at what you've done? That would make a welcome change.

Me:

Couldn't resist.
Carry on.

Can computer-literate people specify a lift, a usual lift, going up and down, stopping at floors etc. using only formal logic?
How far back do you want to start?

I don't know. Could you go back to around 236 BC?

Lift
The earliest known reference to a lift is in the works of the Roman architect Vitruvius, who reported that Archimedes (c. 287 BC – c. 212 BC) built his first lift probably in 236 BC.[2] Some sources from later historical periods mention lifts as cabs on a hemp rope powered by hand or by animals.
In 1000, the Book of Secrets by al-Muradi in Islamic Spain described the use of an lift-like lifting device, in order to raise a large battering ram to destroy a fortress.[3] In the 17th century the prototypes of lifts were located in the palace buildings of England and France. Louis XV of France had a so-called 'flying chair' built for one of his mistresses at the Chateau de Versailles in 1743.[4]
Ancient and medieval lifts used drive systems based on hoists or windlasses. The invention of a system based on the screw drive was perhaps the most important step in lift technology since ancient times, leading to the creation of modern passenger lifts. The first screw drive lift was built by Ivan Kulibin and installed in the Winter Palace in 1793. Several years later another of Kulibin's lifts was installed in the Arkhangelskoye near Moscow.
https://en.wikipedia.org/wiki/Elevator
I was just making sure our brightest minds around here actually didn't know how to do this. Apparently, like you here, they don't even know where to begin.
And, no, I won't give you a lift.
EB

I was just making sure our brightest minds around here actually didn't know how to do this. Apparently, like you here, they don't even know where to begin.
Where would you begin?

I don't know. Could you go back to around 236 BC?

Lift
The earliest known reference to a lift is in the works of the Roman architect Vitruvius, who reported that Archimedes (c. 287 BC – c. 212 BC) built his first lift probably in 236 BC.[2] Some sources from later historical periods mention lifts as cabs on a hemp rope powered by hand or by animals.
In 1000, the Book of Secrets by al-Muradi in Islamic Spain described the use of an lift-like lifting device, in order to raise a large battering ram to destroy a fortress.[3] In the 17th century the prototypes of lifts were located in the palace buildings of England and France. Louis XV of France had a so-called 'flying chair' built for one of his mistresses at the Chateau de Versailles in 1743.[4]
Ancient and medieval lifts used drive systems based on hoists or windlasses. The invention of a system based on the screw drive was perhaps the most important step in lift technology since ancient times, leading to the creation of modern passenger lifts. The first screw drive lift was built by Ivan Kulibin and installed in the Winter Palace in 1793. Several years later another of Kulibin's lifts was installed in the Arkhangelskoye near Moscow.
https://en.wikipedia.org/wiki/Elevator
I was just making sure our brightest minds around here actually didn't know how to do this. Apparently, like you here, they don't even know where to begin.
And, no, I won't give you a lift.
EB
How do you arrive - logically - at the conclusion the brightest minds around here do not know how to do this?

Surely other possibilities logically exist, e.g. :-

A) They have not read your post,

B) They cannot be arsed.

Can computer-literate people specify a lift, a usual lift, going up and down, stopping at floors etc. using only formal logic?
Given that I have done just that using Boolean logic (which is a subset of formal logic) - yes. The top level (application level, or "which floor to go to next") is easy. The lower levels (motor control, accel/decel control, level control) is just as doable but nearly impossible to express in formal logic. Easy in mathematics, though.

the use of an lift-like lifting device

"a Lift-like"
not AN lift-like!

The invention of a system based on the screw drive was perhaps the most important step in lift technology since ancient times,

https://en.wikipedia.org/wiki/Barbegal_aqueduct_and_mill

https://en.wikipedia.org/wiki/Barbegal_aqueduct_and_mill#/media/File:Musée_de_l'Arles_antique,_Arles,_France_(16168385326).jpg
The mills operated from the end of the 1st century until about the end of the 3rd century.[2] The capacity of the mills has been estimated at 4.5 tons of flour per day, enough to supply bread for as many as 10,000[3] of perhaps 30-40,000 inhabitants of Arelate at that time.[4]

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Given that I have done just that using Boolean logic (which is a subset of formal logic) - yes.
Any chance you actually show the result here?
The top level (application level, or "which floor to go to next") is easy. The lower levels (motor control, accel/decel control, level control) is just as doable but nearly impossible to express in formal logic. Easy in mathematics, though.
What do you mean "nearly" impossible"? Do you mean you haven't done it but that it's doable? Is there any impossibility in principle?
EB

How do you arrive - logically - at the conclusion (...)
How do you arrive logically at the conclusion that I arrived at my conclusion logically?
Go on, you first.
EB

I was just making sure our brightest minds around here actually didn't know how to do this. Apparently, like you here, they don't even know where to begin.
You include yourself in this, no doubt.

Can computer-literate people specify a lift, a usual lift, going up and down, stopping at floors etc. using only formal logic?
I'm interested in the principle, no need to get all fussy about it. The simpler the better.
No algorithm allowed. Only ordinary logic.

I can't be too sure, because the question is a little vague, but it looks like it's asking for a specification which corresponds to a static data structure rather than a computer program as such.

The data structure would necessarily be some kind of switching network. Each lift would have a number of inputs and a number of outputs (different floors).
In fact it would be relatively easy to define such a structure once all the floors and all the interconnecting lifts are given.

If I was given this problem I think I could probably have a solution in a day or so; a diagram of the network and a data structure in some language.

Why someone might think this is an example of some kind of logic fail, I can't really say. If someone is keen on finding an example that defies logical description (a physical example), I'd say they're shit out of luck.

Impossible....

I’m not sure if this guy fixes elevators, has terrible luck, or just a death wish.

Can computer-literate people specify a lift, a usual lift, going up and down, stopping at floors etc. using only formal logic?
I'm interested in the principle, no need to get all fussy about it. The simpler the better.
No algorithm allowed. Only ordinary logic. Conjunctions and such, two truth values only, etc.
EB
I hope i am not getting this wrong. Lift consist of steel wire, motor and switch. So for floor 1 length of wire is x. For floor 2 length of wire is x minus something and so on.so what i would do is calculate the revolution of motor w.r.t. floor 1,2 n so on and assign that revolution for floors.

Can computer-literate people specify a lift, a usual lift, going up and down, stopping at floors etc. using only formal logic?
I'm interested in the principle, no need to get all fussy about it. The simpler the better.
No algorithm allowed. Only ordinary logic. Conjunctions and such, two truth values only, etc.
EB

For that kind of machinery (a lift is a very simple machine), you start by creating a Karnaugh table.
There are rules that permit to simplify this table.
Once simplified, you can write the "logic formula" that express all the permitted logical states.

The Use of Karnaugh Map
Now that we have developed the Karnaugh map with the aid of Venn diagrams, let’s put it to use. Karnaugh maps reduce logic functions more quickly and easily compared to Boolean algebra. By reduce we mean simplify, reducing the number of gates and inputs.

We like to simplify logic to a lowest cost form to save costs by elimination of components. We define lowest cost as being the lowest number of gates with the lowest number of inputs per gate.

Given a choice, most students do logic simplification with Karnaugh maps rather than Boolean algebra once they learn this tool.