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This argument is the most common fallacy I see in programming language discussions. I might as well give it a name right here: "Turing equivalence fallacy" or p

This argument is the most common fallacy I see in programming language discussions. I might as well give it a name right here: "Turing equivalence fallacy" or perhaps "syntax sugar fallacy." All Turing Complete programming languages are Turing equivalent to one another. Programs written in one language can be mechanically transformed into those written in another. This is irrelevant to the discussion of programming languages. The whole point of creating different programming languages is to explore different ways to express the same program!

Hirrolot 2y ago
In programming language design, we tend to distinguish between global and local analysis. While type checking and elaboration is an example of global analysis, desugaring is inherently local to some piece of code. Therefore, "power" or "expressiveness" usually mean that something cannot be syntactically "expanded"; e.g., while type classes elaborate into explicit dictionaries, they still require information from the type checker, and therefore considered a "real" feature of a programming language. On the other hand, nested pattern matching can be formulated as local syntax transformation, and therefore it doesn't bring anything fundamentally new to the type system or dynamic semantics. There's also a great talk on the matter [1], if somebody is interested in formalities. [1] https://www.youtube.com/watch?v=43XaZEn2aLc https://www.youtube.com/watch?v=43XaZEn2aLc
- mitt_romney_12 2y ago
  You're approaching this from a PL design standpoint where the distinction is important, but from a user perspective it doesn't matter if it's just "syntax sugar" or if it's a super complicated to implement all that matters is whether the feature is available or not.
  - Hirrolot 2y ago
    Typing features affect the way we design APIs. Libraries written in languages with type classes and without them can have completely different designs. If nested pattern matching is not available, this will not affect the APIs, only the function bodies -- because desugaring is local by definition.
    - chongli 2y ago
      That doesn't matter in practice. If two programming languages have the same underlying feature but one has syntactic sugar to make it very easy to use and the other does not (so is quite cumbersome to use) then you'll find that the library ecosystem for the former language will see the feature in widespread use whereas the ecosystem of the latter will tend to shun the feature. This is one of the social factors of programming language design and it's one of the main reasons successful programming languages work so hard to establish a coherent philosophy and a set of best practices or idioms within the language. For similar reasons, I believe this is why "anything goes" languages such as LISP have struggled to gain widespread adoption: with no philosophy every programmer becomes an island unto themselves.
      - Hirrolot 2y ago
        Yes, features that are easy to use will be more often used, while inconvenient features will be less used. I don't quite see any controversy with my comment.
        chongli 2y ago
        The point is that in both cases the underlying feature is present, so APIs will be compatible. However, the lack of syntactic sugar in the one case will make any API that uses the feature cumbersome to use in that language, so in practice it will be avoided.
      - lispm 2y ago
        > "anything goes" languages such as LISP have struggled to gain widespread adoption: with no philosophy every programmer becomes an island unto themselves. There are already two misconceptions. First: "Lisp has no programming philosophies" and styles. Not every program starts by zero. Since Lisp exists since the end 1950s, it has seen quite a lot in programming styles over the years and it may contain traces of several. Generally it may support more than one programming paradigm. For example during the Common Lisp standardization there was a wish to have a standardized object system. So instead of the multiple possible approaches (actors, message passing, prototype-based, ...), Common Lisp has just one: CLOS, the Common Lisp Object System. So, much of the object-oriented code written in CL is implemented in one particular object system: CLOS. Object Lisp, Flavors, LOOPs, Common Objects, and a bunch of other once had thus been replaced by one standard. CLOS also defines a bunch of user-level macros: DEFCLASS, DEFMETHOD, DEFGENERIC, ... Everyone using CL & CLOS will use those macros. Second: "every programmer becomes an island unto themselves". If we look at the way CLOS was designed: there was a core group of six people from three companies. Around that there was a mailing-list based communication with a large group of interested people. Early on a prototype was implemented as a portable implementation of CLOS. This was widely distributed among interested parties: implementors, companies, research groups, ... Then reports about the language extension and its layers were published, books were published, application & library code was published. One of famous books coming out of this effort: "The Art of the Meta-Object Protocol". It contained also a toy implementation of CLOS in Common Lisp. Book and the implementation of CLOS (both the larger prototype and the toy implementation) showed in excellent quality how to write object-oriented Lisp code. https://mitpress.mit.edu/9780262610742/the-art-of-the-metaobject-protocol/ https://mitpress.mit.edu/9780262610742/the-art-of-the-metaob... So, there are communities, which share code and coding styles. Not every programmer is alone and starts from zero.
gpderetta 2y ago
> Turing equivalence fallacy Better known as the Turing Tar Pit.
OskarS 2y ago
Of course the syntax sugar is a good thing if it makes it easier to write the code, but if the question is about "expressive power of the type system", it's not really relevant: Zig's type system can properly express a sum type. In addition: pattern matching is orthogonal to ADT, you can have pattern matching in both languages with and without algebraic types. Neither one implies the other.
- anon-3988 2y ago
  > Zig's type system can properly express a sum type. Surely any Turing complete PL can express a sum type? I can't imagine a language that can support products but not sums.
  - Tainnor 2y ago
    Turing completeness has nothing to do with static type checking. Dynamically typed PLs can't express any type (except Any) yet are still Turing complete.

Hirrolot 2y ago

In programming language design, we tend to distinguish between global and local analysis. While type checking and elaboration is an example of global analysis, desugaring is inherently local to some piece of code. Therefore, "power" or "expressiveness" usually mean that something cannot be syntactically "expanded"; e.g., while type classes elaborate into explicit dictionaries, they still require information from the type checker, and therefore considered a "real" feature of a programming language. On the other hand, nested pattern matching can be formulated as local syntax transformation, and therefore it doesn't bring anything fundamentally new to the type system or dynamic semantics. There's also a great talk on the matter [1], if somebody is interested in formalities. [1] https://www.youtube.com/watch?v=43XaZEn2aLc https://www.youtube.com/watch?v=43XaZEn2aLc

mitt_romney_12 2y ago
You're approaching this from a PL design standpoint where the distinction is important, but from a user perspective it doesn't matter if it's just "syntax sugar" or if it's a super complicated to implement all that matters is whether the feature is available or not.
- Hirrolot 2y ago
  Typing features affect the way we design APIs. Libraries written in languages with type classes and without them can have completely different designs. If nested pattern matching is not available, this will not affect the APIs, only the function bodies -- because desugaring is local by definition.
  - chongli 2y ago
    That doesn't matter in practice. If two programming languages have the same underlying feature but one has syntactic sugar to make it very easy to use and the other does not (so is quite cumbersome to use) then you'll find that the library ecosystem for the former language will see the feature in widespread use whereas the ecosystem of the latter will tend to shun the feature. This is one of the social factors of programming language design and it's one of the main reasons successful programming languages work so hard to establish a coherent philosophy and a set of best practices or idioms within the language. For similar reasons, I believe this is why "anything goes" languages such as LISP have struggled to gain widespread adoption: with no philosophy every programmer becomes an island unto themselves.
    - Hirrolot 2y ago
      Yes, features that are easy to use will be more often used, while inconvenient features will be less used. I don't quite see any controversy with my comment.
      - chongli 2y ago
        The point is that in both cases the underlying feature is present, so APIs will be compatible. However, the lack of syntactic sugar in the one case will make any API that uses the feature cumbersome to use in that language, so in practice it will be avoided.
    - lispm 2y ago
      > "anything goes" languages such as LISP have struggled to gain widespread adoption: with no philosophy every programmer becomes an island unto themselves. There are already two misconceptions. First: "Lisp has no programming philosophies" and styles. Not every program starts by zero. Since Lisp exists since the end 1950s, it has seen quite a lot in programming styles over the years and it may contain traces of several. Generally it may support more than one programming paradigm. For example during the Common Lisp standardization there was a wish to have a standardized object system. So instead of the multiple possible approaches (actors, message passing, prototype-based, ...), Common Lisp has just one: CLOS, the Common Lisp Object System. So, much of the object-oriented code written in CL is implemented in one particular object system: CLOS. Object Lisp, Flavors, LOOPs, Common Objects, and a bunch of other once had thus been replaced by one standard. CLOS also defines a bunch of user-level macros: DEFCLASS, DEFMETHOD, DEFGENERIC, ... Everyone using CL & CLOS will use those macros. Second: "every programmer becomes an island unto themselves". If we look at the way CLOS was designed: there was a core group of six people from three companies. Around that there was a mailing-list based communication with a large group of interested people. Early on a prototype was implemented as a portable implementation of CLOS. This was widely distributed among interested parties: implementors, companies, research groups, ... Then reports about the language extension and its layers were published, books were published, application & library code was published. One of famous books coming out of this effort: "The Art of the Meta-Object Protocol". It contained also a toy implementation of CLOS in Common Lisp. Book and the implementation of CLOS (both the larger prototype and the toy implementation) showed in excellent quality how to write object-oriented Lisp code. https://mitpress.mit.edu/9780262610742/the-art-of-the-metaobject-protocol/ https://mitpress.mit.edu/9780262610742/the-art-of-the-metaob... So, there are communities, which share code and coding styles. Not every programmer is alone and starts from zero.

gpderetta 2y ago

> Turing equivalence fallacy Better known as the Turing Tar Pit.

OskarS 2y ago

Of course the syntax sugar is a good thing if it makes it easier to write the code, but if the question is about "expressive power of the type system", it's not really relevant: Zig's type system can properly express a sum type. In addition: pattern matching is orthogonal to ADT, you can have pattern matching in both languages with and without algebraic types. Neither one implies the other.

anon-3988 2y ago
> Zig's type system can properly express a sum type. Surely any Turing complete PL can express a sum type? I can't imagine a language that can support products but not sums.
- Tainnor 2y ago
  Turing completeness has nothing to do with static type checking. Dynamically typed PLs can't express any type (except Any) yet are still Turing complete.