Option C. The value NaN compares unequal to every value, even itself. This breaks one of the rules of what equality even means (that every value must be equal to itself, the “reflexivity” axiom). It is for this reason (among others, equality “partial” equivalence between values of different types? 🤮) Rust needed to have PartialEq. See IEEE 754 for more details.

Why typeof null is "object"? Because it is defined so: https://tc39.es/ecma262/multipage/ecmascript-language-expressions.html#sec-typeof-operator

5. If val is null, return "object".

As for the rationale behind the choice, it might have something to do with “Prototypal inherience” the language has. https://tc39.es/ecma262/multipage/overview.html#sec-objects

Every object created by a constructor has an implicit reference (called the object’s prototype) to the value of its constructor’s “prototype” property. Furthermore, a prototype may have a non-null implicit reference to its prototype, and so on; this is called the prototype chain.

We can understand this to mean that prototype chains are null terminated ;)

For example:

> Object.getPrototypeOf({}) === Object.prototype
true
> Object.getPrototypeOf(Object.getPrototypeOf({}))
null
> Object.getPrototypeOf(null)        TypeError: not an object

Uhh…

Now, let’s go to some abstract algebra. All good (closed) binary operations we deal with have an identity or neutral value. For example: addition has 0, multiplication has 1, boolean and has true, boolean or or xor has false. Performing these operations with the neutral value does not change the other operand: for example, x + 0 == x, a * 1 == a, true && b == b and so on. If you admit min and max as operators, you can see why ∞ and -∞ are the neutral values, respectively: min(∞, x) == x and max(-∞, y) == y for every (real) value of x and y. Observe how Array.prototype.reduce works (with its second argument) for inspiration on why and how all this matters: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce

For mathematicians: closed, because the operators are maps S × S →S, to exclude <, > etc. as they map to Bool. Oh, they are relations, bla bla … real numbers, we don’t want to deal with other total orders here, there should be some way to call orders that have both top and bottom values, complex numbers don’t have orders (usual ones, are there unusual ones?), bla bla bla

As for the last one, sigh… https://tc39.es/ecma262/multipage/abstract-operations.html#sec-islooselyequal

Oh, that !s in there aren’t boolean not… they are… (looks it up) argh, read it yourself https://tc39.es/ecma262/multipage/notational-conventions.html#sec-returnifabrupt-shorthands

On mobile devices, text markup languages are the way to go. Viewing office suite documents is enough… editing them is not easy. I have used groff, tex and latex, and typst recently (on Termux, obviously) with various degrees of success. I wonder when we will have FOSS apps that are as usable or more than Google’s Docs and Sheets.

If your PDF viewer supports re-reading when file is changed (or reloading file every time app comes to foreground, I suppose), typst watch and that viewer open is the closest to a WYSIWYG I could get working.

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I tend to believe that there is a sort of “natural distribution” of possible outcomes where there is scope for that, i.e. allowing randomness. Unless we can construct a way to derive this out of some natural laws, positive outcome for everyone sounds like to have very little chance to happen.

Related, whenever people ask me how I am, the usual reply is “I am alive”.