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Whenever I see a new programming language, this list of questions by Frank Atanassow comes to mind: 1. What problem does this language solve? How can I mak

Whenever I see a new programming language, this list of questions by Frank Atanassow comes to mind: 1. What problem does this language solve? How can I make it precise? 2. How can I show it solves this problem? How can I make it precise? 3. Is there another solution? Do other languages solve this problem? How? What are the advantages of my solution? of their solution? What are the disadvantages of my solution? of their solution? 4. How can I show that my solution cannot be expressed in some other language? That is, what is the unique property of my language which is lacking in others which enables a solution? 5. What parts of my language are essential to that unique property? Do read the whole post (http://lambda-the-ultimate.org/node/687#comment-18074 http://lambda-the-ultimate.org/node/687#comment-18074), it has lots of elaboration on these questions. From a skim of the Bel materials, I couldn't answer these questions. Maybe PG or someone else can take a stab at the answer?

capableweb 7y ago
I think you're unable to answer those questions as the language does not seem to aim to try to offer any answer to those questions. Bel seems to be an experiment, and maybe once the "specification" phase has been done, some of those questions could be answered. Here is the relevant parts from the language document: > Bel is an attempt to answer the question: what happens if, instead of switching from the formal to the implementation phase as soon as possible, you try to delay that switch for as long as possible? If you keep using the axiomatic approach till you have something close to a complete programming language, what axioms do you need, and what does the resulting language look like? > I want to be clear about what Bel is and isn't. Although it has a lot more features than McCarthy's 1960 Lisp, it's still only the product of the formal phase. This is not a language you can use to program computers, just as the Lisp in the 1960 paper wasn't. Mainly because, like McCarthy's Lisp, it is not at all concerned with efficiency. When I define append in Bel, I'm saying what append means, not trying to provide an efficient implementation of it.
rjyoungling 7y ago
That's fair, but I love PG so I'm biased lol
pg 7y ago
I think the point of a high-level language is to make your programs shorter. All other things (e.g. libraries) being equal, language A is better than language B if programs are shorter in A. (As measured by the size of the parse tree, obviously, not lines or characters.) The goal of Bel is to be a good language. This can be measured in the length of programs written in it. Lisp dialects have as a rule been good at making programs short. Bel is meant to do the same sorts of things previous dialects have, but more so. It's also meant to be simple and clear. If you want to understand Bel's semantics, you can read the source.
- agumonkey 7y ago
  Hello, do you think you could find time make a table of content ? I like .txt files but a language spec is just a tad too long. Or maybe for the lispers around have a short summary of what was inspiring you to make bel after arc ? what were your ideas, problems (beside making programs more expressive shorter). Thanks
- cousin_it 7y ago
  Thanks for the response! Which features of Bel do you think will contribute the most to making programs shorter or clearer, compared to other Lisp dialects?
  - pg 7y ago
    It's so broadly the goal of the language that many things do, often in small ways. For example, it turns out to be really convenient that strings are simply lists of characters. It means all the list manipulation functions just work on them. And the where special form and zap macro make it much easier to define operators that modify things. The advantage of Bel is a lot of small things like that rather than a single killer feature. Making bel.bel shorter was one of my main goals during this project. It has a double benefit. Since the Bel source is a Bel program, the shorter I can make it, the more powerful Bel must be. Plus a shorter source is (pathological coding tricks excepted) easier to understand, which means Bel is better in that way too. There were many days when I'd make bel.bel 5 lines shorter and consider it a successful day's work. One of the things I found helped most in making programs shorter was higher order functions. These let you get rid of variables, which are a particularly good thing to eliminate from code when you can. I found that higher order functions combined with intrasymbol syntax could often collapse something that had been a 4 line def into a 1 line set.
danmg 7y ago
If it's a language for general programming, I immediately ask if it has sum/product types, pattern matching, and static typing. I'm not really interested in learning yet another dynlang that is missing all those.
- nuclearnice1 7y ago
  What are sum/product types?
  - wbradley 7y ago
    https://en.m.wikipedia.org/wiki/Algebraic_data_type https://en.m.wikipedia.org/wiki/Algebraic_data_type
  - chrisseaton 7y ago
    In terms of C, a sum is a union and a product is a struct.
wyldfire 7y ago
Maybe Bel is Blub?
dplgk 7y ago
Can this language render block quotes correctly on mobile in HN? Then I think it's a real win.
mattknox 7y ago
These questions aren't useful for evaluating pg's work (or frankly that of most PL implementors) because it concerns things, like syntax, libraries, user culture, etc., that is outside of the rather narrow domain Atanassow cares about. He believes languages are utterly defined by their type systems, saying in the LtU comment you linked: "Perl, Python, Ruby, PHP, Tcl and Lisp are all the same language". I'd assume that he would say the same about js, lua, etc.. AFAICT, he's quite knowledgeable about PLT, formal methods, static typing, category theory, etc., but he disregards everything else. It's worth considering whether he is right to do so. A waspish answer is to observe that companies built on languages he deems to be "in the corner" (c, java, dynamic languages) constitute the entirety of companies with significant market capitalization, and ask (apologies to Aaron Sorkin) "If your type system is so smart, why do you lose so always". A better answer is to note that a bunch of stuff that he deems trivial (generally anything outside of the type system, but specifically libraries, syntax, bindings to existing systems, etc.) matters, so javascript is different than python despite being identical in his eyes. Specifically, js runs in the browser and has a pretty good runtime for building web services, while python has exceptional ecosystem support for data science and machine learning.
kazinator 7y ago
> How can I show that my solution cannot be expressed in some other language? This is not easy. The solution is certainly computable in other languages, and expressivity is subjective. We can quantify it like this: a solution is highly expressive if it is given in terms of elements mostly from the problem domain. For instance, if we have to "malloc" some memory and bind it to a "pointer", but the problem domain is finance, those things don't have anything to do with the problem domain and are therefore inexpressive. Even if we quantify expressivity, the proposition that "this has the best expressivity for a given problem domain than all other tools, known and unknown" is mired with intractability.

capableweb 7y ago

I think you're unable to answer those questions as the language does not seem to aim to try to offer any answer to those questions. Bel seems to be an experiment, and maybe once the "specification" phase has been done, some of those questions could be answered. Here is the relevant parts from the language document: > Bel is an attempt to answer the question: what happens if, instead of switching from the formal to the implementation phase as soon as possible, you try to delay that switch for as long as possible? If you keep using the axiomatic approach till you have something close to a complete programming language, what axioms do you need, and what does the resulting language look like? > I want to be clear about what Bel is and isn't. Although it has a lot more features than McCarthy's 1960 Lisp, it's still only the product of the formal phase. This is not a language you can use to program computers, just as the Lisp in the 1960 paper wasn't. Mainly because, like McCarthy's Lisp, it is not at all concerned with efficiency. When I define append in Bel, I'm saying what append means, not trying to provide an efficient implementation of it.

rjyoungling 7y ago

That's fair, but I love PG so I'm biased lol

pg 7y ago

I think the point of a high-level language is to make your programs shorter. All other things (e.g. libraries) being equal, language A is better than language B if programs are shorter in A. (As measured by the size of the parse tree, obviously, not lines or characters.) The goal of Bel is to be a good language. This can be measured in the length of programs written in it. Lisp dialects have as a rule been good at making programs short. Bel is meant to do the same sorts of things previous dialects have, but more so. It's also meant to be simple and clear. If you want to understand Bel's semantics, you can read the source.

agumonkey 7y ago
Hello, do you think you could find time make a table of content ? I like .txt files but a language spec is just a tad too long. Or maybe for the lispers around have a short summary of what was inspiring you to make bel after arc ? what were your ideas, problems (beside making programs more expressive shorter). Thanks
cousin_it 7y ago
Thanks for the response! Which features of Bel do you think will contribute the most to making programs shorter or clearer, compared to other Lisp dialects?
- pg 7y ago
  It's so broadly the goal of the language that many things do, often in small ways. For example, it turns out to be really convenient that strings are simply lists of characters. It means all the list manipulation functions just work on them. And the where special form and zap macro make it much easier to define operators that modify things. The advantage of Bel is a lot of small things like that rather than a single killer feature. Making bel.bel shorter was one of my main goals during this project. It has a double benefit. Since the Bel source is a Bel program, the shorter I can make it, the more powerful Bel must be. Plus a shorter source is (pathological coding tricks excepted) easier to understand, which means Bel is better in that way too. There were many days when I'd make bel.bel 5 lines shorter and consider it a successful day's work. One of the things I found helped most in making programs shorter was higher order functions. These let you get rid of variables, which are a particularly good thing to eliminate from code when you can. I found that higher order functions combined with intrasymbol syntax could often collapse something that had been a 4 line def into a 1 line set.

danmg 7y ago

If it's a language for general programming, I immediately ask if it has sum/product types, pattern matching, and static typing. I'm not really interested in learning yet another dynlang that is missing all those.

nuclearnice1 7y ago
What are sum/product types?
- wbradley 7y ago
  https://en.m.wikipedia.org/wiki/Algebraic_data_type https://en.m.wikipedia.org/wiki/Algebraic_data_type
- chrisseaton 7y ago
  In terms of C, a sum is a union and a product is a struct.

wyldfire 7y ago

Maybe Bel is Blub?

dplgk 7y ago

Can this language render block quotes correctly on mobile in HN? Then I think it's a real win.

mattknox 7y ago

These questions aren't useful for evaluating pg's work (or frankly that of most PL implementors) because it concerns things, like syntax, libraries, user culture, etc., that is outside of the rather narrow domain Atanassow cares about. He believes languages are utterly defined by their type systems, saying in the LtU comment you linked: "Perl, Python, Ruby, PHP, Tcl and Lisp are all the same language". I'd assume that he would say the same about js, lua, etc.. AFAICT, he's quite knowledgeable about PLT, formal methods, static typing, category theory, etc., but he disregards everything else. It's worth considering whether he is right to do so. A waspish answer is to observe that companies built on languages he deems to be "in the corner" (c, java, dynamic languages) constitute the entirety of companies with significant market capitalization, and ask (apologies to Aaron Sorkin) "If your type system is so smart, why do you lose so always". A better answer is to note that a bunch of stuff that he deems trivial (generally anything outside of the type system, but specifically libraries, syntax, bindings to existing systems, etc.) matters, so javascript is different than python despite being identical in his eyes. Specifically, js runs in the browser and has a pretty good runtime for building web services, while python has exceptional ecosystem support for data science and machine learning.

kazinator 7y ago

> How can I show that my solution cannot be expressed in some other language? This is not easy. The solution is certainly computable in other languages, and expressivity is subjective. We can quantify it like this: a solution is highly expressive if it is given in terms of elements mostly from the problem domain. For instance, if we have to "malloc" some memory and bind it to a "pointer", but the problem domain is finance, those things don't have anything to do with the problem domain and are therefore inexpressive. Even if we quantify expressivity, the proposition that "this has the best expressivity for a given problem domain than all other tools, known and unknown" is mired with intractability.