Lambda the Ultimate

Interesting. If I'd tried to make a list of imaginable ways to improve a programming language, readability would likely be at the top of my list; if, indeed, I went on to attempt a lengthy list rather than, say, just remarking on the desirability of readability. Thought-provoking, that readability wasn't on your list (sic: neither good nor bad; thought-provoking). To my mind, the purpose of a programming language is to express what we want done, hence lucidity is a core value.

Readability is not a property that I would attribute to a language, because it's as much a function of the reader (familiarity with language, libraries, patterns, problem domain, etc.) as of notation or tooling.

But those cognitive dimensions of notation do contribute to readability. I mentioned one of them, consistency, then the set as a whole.

Aside: There is also much that tooling can do to enhance a human's ability to explore and understand a codebase, e.g. good fonts, syntax highlighting, jump-to-definition, progressive disclosure, in-place tutorials or spreadsheet-like unit-tests. How much should be under the umbrella of 'readability'?

Just taking one point there that I found thought-provoking: I suggest the perception that anything simple must be a toy may be a consequence of the paradigm we're imposing on the subject.

This aspect of scientific paradigms can be tricky, so pardon if I repeat familiar territory (from Kuhn's The Structure of Scientific Revolutions). Paradigms at best are immensely valuable because researchers within the paradigm can apply laser focus to exploring the research space within the paradigm, spending absolutely zero resources worrying about alternatives to the paradigm. A tremendous advantage at best, this inevitably suppresses alternatives to the paradigm even if they have merit. Iirc (can't instantly conjure it up), Kuhn remarked in the book that at the time a paradigm is adopted there is already ample evidence that it's wrong. How useful is it to focus research this way? Seemingly, as long as it is advantageous to continue to explore the space of research within the paradigm, the paradigm should continue to be useful. One of the things that can go wrong with this pattern is that a paradigm may continue to look plausible from the inside, while standing back from it one may suspect that really we might do well to look for a better approach.

At the level where we perceive anything simple as a toy, it seems we may really have just one paradigm for programming languages, despite the many so-called "programming language paradigms". If we really need to break out of this paradigm (or mindset, whatever you call it), the thing we're looking for may indeed be extremely simple. (Recalling, notionally, (profundity index of idea) = (difficulty of discovery) times (difficulty of finding a really good explanation) times (obviousness once explained well).)

I do believe you are onto something, and yes, I think that is what I was getting at. In some ways, our industry has repeatedly converted the profound to the obvious, and as we have accreted those advances, the cost of incremental profundity has grown exponentially.

I might add:

• Composition: hard to see how composition would ever go away. Build larger components by composing smaller components.
• Environment/context: Every computation runs in an environment, and many recent advances have been about moving the environment closer to a first-class value, ie. scoped bindings in languages, hardware/software virtual machines, delimited continuations.

Thought-provoking additions to the list. I think I agree about environment/context, which, though its roots may belong to logic, seems to have something of the stamp of programming upon it. Honestly unsure about composition, which might be deemed of an earlier vintage, so not exactly a programming notion. Tracing the origins of foundational ideas can be tricky. E.g., our modern notions of function and variable go back, afaik, to Frege in the latter half of the nineteenth century and belong to logic rather than computation, though admittedly refined by Church who is more of a transitional figure (a former student of his later described him as "logic incarnate"). Now that you've directed attention to these sorts of ideas, another with clear PLT origins that I've lately come to suspect may be crucial far more widely (in mathematics both pure and applied) is first-class value.

Ah, you're looking for concepts that originated from computer science. First-class value is definitely a good candidate then. I think computing merely refined our understanding of the other concepts I mentioned. Other ideas:

• Computational power: the computational power of a system being designed or used as a blackbox can be a meaningful property, ie. whether it's domain-specific/purpose-built or general purpose/Turing complete.
• Encapsulation: some distinction between inside and outside views of an entity seems inescapable, although there is some relationship with environment/context here. Every computer clearly has an internal view that we can only interact with via an external facade.
• Computation's close connection with logic, inference and synthesis: we have type inference and program synthesis (extracting OCaml programs from Coq proofs), and so on. I expect inference/synthesis to become increasingly important over the next century.
• Induction and Coinduction: induction has received a lot of attention and originated outside of CS, but coinduction is only just starting to receive attention and arguably came from CS. Having an abstraction and its dual seems pretty important for expressiveness.

Seems likely. This also seems related to my predilection for exploring exotic hypotheses that challenge conventional wisdom, and perhaps to why my list of fundamental things we've learned is short.