I don’t have 2 mil, how do I get out of this? File for bankruptcy?

A package is reproducible if you use the same inputs, run the build, and get the same outputs.

The issue is that the build can produce different outputs given the same inputs. So you need to modify the build or patch the outputs. This is something that is being worked on by most distributions: https://reproducible-builds.org/who/projects/

NixOS is not special in that regard nor are all NixOS packages reproducible.

Nope, nix doesn’t ensure or require that the builds are deterministic. It’s not any better in that regard than other package managers.

It’s not really fully reproducible either.

The implementations mostly don’t matter. The only thing that you need to get right are the interfaces.

Nope. Monads enable you to redefine how statements work.

Let’s say you have a program and use an Error[T] data type which can either be Ok {Value: T} or Error:

var a = new Ok {Value = 1};
var b = foo();
return new Ok {Value = (a + b)};

Each statement has the following form:

var a = expr;
rest

You first evaluate the “expr” part and bind/store the result in variable a, and evaluate the “rest” of the program.

You could represent the same thing using an anonymous function you evaluate right away:

(a => rest)(expr);

In a normal statement you just pass the result of “expr” to the function directly. The monad allows you to redefine that part.

You instead write:

bind((a => rest), expr);

Here “bind” redefines how the result of expr is passed to the anonymous function.

If you implement bind as:

B bind(Func[A, B] f, A result_expr) {
   return f(result_expr);
}

Then you get normal statements.

If you implement bind as:

Error[B] bind(Func[A, Error[B]] f, Error[A] result_expr) {
   switch (result_expr) {
       case Ok { Value: var a}:
           return f(a);
       case Error:
           return Error;
   }
}

You get statements with error handling.

So in an above example if the result of foo() is Error, the result of the statement is Error and the rest of the program is not evaluated. Otherwise, if the result of foo() is Ok {Value = 3}, you pass 3 to the rest of the program and you get a final result Ok {Value = 4}.

So the whole idea is that you hide the if Error part by redefining how the statements are interpreted.

Some people consider working on programming languages fun, so they create new ones.