Rule Of Three

Survival skills

Prioritizing needs


Humans needs to survive:

  1. Fire
  2. Water
  3. Food

Humans cannot survive:

  1. more than three hours exposed to extremely low temperatures.
  2. more than three days without water.
  3. more than three weeks without food.



Harmonic oscillators (resonant current)
- LCR circuit
- RLC circuit

Electrical circuit connected (series or parallel)
  • L - inductor (input)
  • R - resistor (damping)
  • C - capacitor (storage)

Oscillation induced dies away over time if it is not kept going by a source
Resistance is unavoidable (real circuits)



Code re-factoring
- Determine when a replicated piece of code replaced by a procedure
— copy and paste the code once
— replicated three times, extract into a new procedure.
Duplication is considered harmful and a bad practice (code harder to maintain).
Code changes - change it in all places correctly, error-prone
Code in only one, easily changed.

C++ programming

Class method definitions
Law of The Big Three
The Big Three
- If a class defines one of three functions, it should probably explicitly define all three:

  1. destructor
  2. copy constructor
  3. copy assignment operator

All are special member functions.

If not declared, implicitly implemented by compiler with default semantics on all members of class

  1. Destructor - Destruct object's members
  2. Copy constructor - Construct object's members from equivalent members in copy constructor's parameter
  3. Assignment operator - Assign object's members from equivalent members in assignment operator's parameter


Many things are structured in threes

"Omne trium perfectum" : Latin phrase
- "everything that comes in threes is perfect", or
- "every set of three is complete"


Writing principle
Things that come in threes are inherently "better" than other numbers of things

Reader/audience likely to consume information written in groups of threes
- Eamples
— "Go, fight, win!" (slogan)
— The Three Stooges
— The Three Musketeers
— Three Little Pigs
— Three Billy Goats Gruff
— Goldilocks and the Three Bears
— Three Blind Mice

Series of three progression
- tension created
- tension built up
- tension released

Adjective groupings for emphasis
- Ex., 'very, very, very'


Composition rule (Rule of thirds)
Visual arts (painting, photography, design)

Image imagined as divided into nine equal parts
- two equally-spaced horizontal lines
- two equally-spaced vertical lines

Important compositional elements laced along lines or intersections
- aligning with points creates tension, energy and interest

Air and sea


Scuba divers' Rule of thirds
Plan dives so not to consume all breathing gas from diving cylinder before end of the dive.

Gas supply

  1. one third - outward journey
  2. one third - return journey
  3. one third - safety reserve

Other's higher breathing rate and/or different volume of gas
- set one third of other's gas supply as remaining 'third'
- turn point to exit is earlier
- lower breathing rate carries larger volume of gas

Reserves needed (overhead environment)
- used if gone deeper or longer than planned
- used if decompression stops surfacing safely
- allows donation of gas to out-of-gas diver


"3:1 rule of descent"
- 3 miles of travel for every 1000 feet descent

Unpressurized aircraft
- Allow adapt to pressure changes (depressurize) comfortably
- Slow, steady, and comfortable descent profile

Pressurized aircraft
- cabin pressure descent rate no more than ~600 feet per minute



Three-body problem
- physics and classical mechanics
- unstable trajectories and probability
- special case of the n-body problem

Simplest mechanical system
- Atomic systems (atoms, ions, molecules)
- cluster of galaxies
- Planetary systems (star(s), planets, and their satellites)

Moon, the Earth and the Sun
- Positions, masses and velocities data set (directly or indirectly) of three bodies in time
- Determine the motions of the three bodies
- Find positions at times with laws of classical mechanics (Newton's laws of motion and of universal gravitation)

Motion of three particles models
- particles are considered as point masses, neglecting shape and internal structure
- interaction is a scalar potential (gravity or electromagnetism)

Quantum approximations
- Perturbation theory
- 2-body problem plus additional deviation forces

N-body problem approximations
- analytical solution (convergent power series)
— useless for practical purposes
- approximate solution by numerical analysis
— numerical integration
— classical trigonometric series


Computation method (Indian-Vedic and Chinese mathematicians)
Particular form of cross multiplication
Equation form: (a/b) = (c/x)
Variable evaluated (right-hand denominator): x = (bc)/a


Business and Economics
Competitors in market
Explains mature competitive markets three 'major players'
- Will be three major competitors in free markets within any one industry
Industries with exactly three generalists outperformed every other industry structure
Other than the three major competitors, businesses only succeed if able to operate in a niche market

First-ranked competitors - Least innovative, 'steal' ideas
Second-ranked competitors - "Sweet spot"
Third-ranked competitors - Price wars drive them out of business, new entity reemerge
Niche-market specialists - Most innovative

Market share best performance graph
- small, niche-market specialists (1% - 5% market share) - slopes downward
- large, full-line generalists (over 10% market share) - slopes upwards

Competitors in between the two performed poorly (“the ditch”);
- micro-specialists, excessive market share generalists, and strategic weak firms underperform others


Calculated confidence limit (no events observed)
If no major adverse events in a group of n people, 95% confidence that chance of major adverse events is less than one in n / 3 (or equivalently, less than 3 in n)
- approximate result, good when n > 30



Christian monotheism doctrine of The Great Spirit
- Christian faith "mystery"

- three distinct divine persons
— Father
— Son
— Holy Spirit

- Co-equal
- Co-eternal
- Consubstantial

Three-fold Law

Law of Return
Wicca religious tenet (not universal)
- Energy puts out into the world, positive or negative, is returned to that person three times.
Reward or punishment tied to one's actions

- Ethics of reciprocity
— karma (Dharmic religions)
— "Do unto others as you would have them do unto you" (Christian edict, Matthew 7:12; "Golden Rule.")

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