Chaos theory

When the present determines the future, but the approximate present does not approximately determine the future. - Edward Lorenz

Code

If you can’t write it down in English, you can’t code it - Peter Halpern, via Jon Bentley

Prioritize

There is no such thing as two equally urgent projects, only priorities that haven’t been made clear yet. - Unknown

Regular expression

Some people, when confronted with a problem, think “I know, I’ll use regular expressions.” Now they have two problems. - Jamie Zawinski

Science

When people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together. - Isaac Asimov

Writing about why Emacs is hard for new users, I can’t help but think back to how important it is to name things well. This is not the first time I tried to write about this idea. I don’t think I’ve ever done a great job at it.

The thing is, naming things is really the most important way we capture ideas. Every single word we learn is an idea that has been captured and named. Let’s set aside that an idea like “cow” may mean different things to different people – that is a discussion to have elsewhere. The point I’m making is that you have now named some thing “cow” and you can use it in your thought process. Now you can in your mind imagine what a cow might when it is surrounded by predators. You might imagine what a cow might do in a crowd of people. You might imagine how that cow might behave differently based on how you and other people behave around it. You can do this because you have given a useful definition to the word “cow”. In a similar vein, useful definitions and words can help you think more clearly and hopefully, make better decisions.

bind

Sometimes a synonym for “map”

conflate

combine

disjoint

separate, e.g., odd numbers and even numbers are disjoint

disjunction

inclusive or – if one of the inputs is True

extrinsic

not intrinsic

federated

Top-down delegation of responsibilities; Has a single point of failure at the top.

PID controller

control loop feedback mechanism

e.g., curise control

99%ile

Abbreviation of percentile

EBNF

Extended Backus-Naur Form

Useful for defining the syntax of a programming language

EBNF terminal

a token/word/chunk in EBNF

Alpha

Αα

Beta

Ββ

Gamma

Γγ

Delta

Δδ

Commonly denotes ‘difference’

Epsilon

Εε

Used in Greedy-Epsilon algo for multi-armed bandit problems

Error margin in floating point comparisons.

Zeta

Ζζ

Eta

Ηη

Theta

Θθ

Iota

Ιι

Kappa

Κκ

Lambda

Λλ

Mu

Μμ

Nu

Νν

Xi

Ξξ

Omicron

Οο

Pi

Ππ

Rho

Ρρ

Sigma

Σσς

Tau

Ττ

Upsilon

Υυ

Phi

Φφ

Chi

Χχ

Psi

Ψψ

Union

∪

Aleph

ℵ

Symbol for cardinal numbers. ℵ is pronounced as Aleph-null.

Empty Set

∅

Such That

Commonly represented as a colon, :

Example, D={x^2|x ∈ N, x >=1, x <= 4}. This reads D is the set of all x^2 SUCH THAT: 1) x is a natural number; 2) x is greater or equal to 1; 3) x is less than or equal to 4.

Intersection

∩

Subset

⊂ or ⊆

e.g., if A = {1,4,9} and B = {1,4}, then B ⊂ A (B is a subset of A).

Belongs To

∈

∉ Means “not belong”.

To say that 1 belongs to S, we write 1 ∈ S.

e.g., if A = {1,4,9} and e = 4, then we say e∈A, meaning “e belongs to A”. However, one would not say e⊂A – e is a single element, not a set. Similarly, if B = {1,4}, one would not say B∈A or “B belongs to A”, as B is a set not a single element.

Complements

Difference between two sets

Relative Complement

A\B means objects that belong to A and not to B. i.e., {1,2,3}{3} == {1,2}

Omega

Ωω

P(A|B)

The likelihood of event A occurring given that B is true.

P(A^C)

The probability that A doesn’t happen

Precision Recall

Precision = probability that some retreived doc is relevant; Recall = probability that some relevant doc was retreived.

Narrow Integration Tests

exercise only that portion of the code in a service that talks to a separate service; uses test doubles of those services, either in process or remote; thus consist of many narrowly scoped tests, often no larger in scope than a unit test (and usually run with the same test framework that’s used for unit tests)

Broad Integration Tests

require live versions of all services, requiring substantial test environment and networ access; exercise code paths through all services, not just code responsible for interactions

Balanced Binary Search Tree

For example, red-black tree or AVL tree.

Natural Numbers

ℕ

double-struck N

Cardinal numbers,

Complex Numbers

ℂ

double-struck C

Related

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