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> ... “dynamic types” are, at their core, there to make unit testing less tedious, and are a tool for finding bugs. I don't think this is a good description of

> ... “dynamic types” are, at their core, there to make unit testing less tedious, and are a tool for finding bugs. I don't think this is a good description of dynamic typing. I'd probably go with something more like, dynamic typing is a way to defer until runtime typing aspects of the program's implementation. I suppose dynamic typing does make unit testing easier, among other things, but it feels wrong to say it's "for" that. A car is for getting one or more people from point A to B. It also has a radio, but a car is not "for" listening to the radio.

naasking 7y ago
> I suppose dynamic typing does make unit testing easier, among other things, but it feels wrong to say it's "for" that. The summary is trying to say that that's dynamic typing's primary advantage. Any other advantage you'd care to ascribe to dynamic typing is not intrinsic to dynamic typing itself.
- ridiculous_fish 7y ago
  The whole article seems concerned with the testability and bug-finding nature of types. But the main strength of dynamic types is the ability to defer decisions until runtime. JS isn't dynamically typed to make testing easier. JS uses dynamic types because you couldn't build the web any other way.
  - naasking 7y ago
    > But the main strength of dynamic types is the ability to defer decisions until runtime. That's not a strength. Deferring until runtime only that which must be deferred is a strength, but that's not one exhibited by dynamically typed languages. It is one that's available to statically typed languages though, like C# and now even Haskell has a deferred typing mode. > JS uses dynamic types because you couldn't build the web any other way. That's patently false. The whole engine running every browser is statically typed. There are libraries for working with the full DOM in HTML documents for Java, C# and other typed languages.
    - ridiculous_fish 7y ago
      Obviously the ability to defer decisions to runtime is a strength - how could you possibly dispute that? And yes statically typed languages have this strength if they use dynamic types. The article's point is that static and dynamic types are fundamentally unrelated to each other. Many languages can and do use both. When you make a web page you have no idea what "only must" be deferred. There's no way to enforce that the JS you write today will be statically compatible with the libraries and browsers that it touches tomorrow. That's why JS uses dynamic types. > That's patently false. The whole engine running every browser is statically typed My point is not about building web browsers, it is about building the web. The web has JS which must coexist with arbitrary other JS, running on many different browsers with many more versions. How could you possibly build this without dynamic typing?
      - naasking 7y ago
        > The article's point is that static and dynamic types are fundamentally unrelated to each other Not unrelated. You can embed dynamic types into a statically typed language, but not vice versa. Formerly dynamically typed languages that pull in static types, like Racket or TypeScript, become statically typed languages with embedded dynamic types. > There's no way to enforce that the JS you write today will be statically compatible with the libraries and browsers that it touches tomorrow This has nothing to do with dynamic types but with standardisation. C# is a language that is considerably different from its first release, and yet v1.0 C# still compiles on the latest compiler. The converse is not true, for either JS or C#. Dynamic types don't help with this problem. > The web has JS which must coexist with arbitrary other JS, running on many different browsers with many more versions. How could you possibly build this without dynamic typing? How do all the arbitrary programs on your computer coexist? The programs that interact do so via protocols or standard interfaces, and the ones that don't interact are isolated. This is no different than any other software.
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        7y ago
dllthomas 7y ago
> dynamic typing is a way to defer until runtime typing aspects of the program's implementation That's more of a "how", where the bit you quoted seemed to be speaking to "why", IMO.

naasking 7y ago

> I suppose dynamic typing does make unit testing easier, among other things, but it feels wrong to say it's "for" that. The summary is trying to say that that's dynamic typing's primary advantage. Any other advantage you'd care to ascribe to dynamic typing is not intrinsic to dynamic typing itself.

ridiculous_fish 7y ago
The whole article seems concerned with the testability and bug-finding nature of types. But the main strength of dynamic types is the ability to defer decisions until runtime. JS isn't dynamically typed to make testing easier. JS uses dynamic types because you couldn't build the web any other way.
- naasking 7y ago
  > But the main strength of dynamic types is the ability to defer decisions until runtime. That's not a strength. Deferring until runtime only that which must be deferred is a strength, but that's not one exhibited by dynamically typed languages. It is one that's available to statically typed languages though, like C# and now even Haskell has a deferred typing mode. > JS uses dynamic types because you couldn't build the web any other way. That's patently false. The whole engine running every browser is statically typed. There are libraries for working with the full DOM in HTML documents for Java, C# and other typed languages.
  - ridiculous_fish 7y ago
    Obviously the ability to defer decisions to runtime is a strength - how could you possibly dispute that? And yes statically typed languages have this strength if they use dynamic types. The article's point is that static and dynamic types are fundamentally unrelated to each other. Many languages can and do use both. When you make a web page you have no idea what "only must" be deferred. There's no way to enforce that the JS you write today will be statically compatible with the libraries and browsers that it touches tomorrow. That's why JS uses dynamic types. > That's patently false. The whole engine running every browser is statically typed My point is not about building web browsers, it is about building the web. The web has JS which must coexist with arbitrary other JS, running on many different browsers with many more versions. How could you possibly build this without dynamic typing?
    - naasking 7y ago
      > The article's point is that static and dynamic types are fundamentally unrelated to each other Not unrelated. You can embed dynamic types into a statically typed language, but not vice versa. Formerly dynamically typed languages that pull in static types, like Racket or TypeScript, become statically typed languages with embedded dynamic types. > There's no way to enforce that the JS you write today will be statically compatible with the libraries and browsers that it touches tomorrow This has nothing to do with dynamic types but with standardisation. C# is a language that is considerably different from its first release, and yet v1.0 C# still compiles on the latest compiler. The converse is not true, for either JS or C#. Dynamic types don't help with this problem. > The web has JS which must coexist with arbitrary other JS, running on many different browsers with many more versions. How could you possibly build this without dynamic typing? How do all the arbitrary programs on your computer coexist? The programs that interact do so via protocols or standard interfaces, and the ones that don't interact are isolated. This is no different than any other software.
      - deleted 7y ago
        [deleted]
      - 7y ago

dllthomas 7y ago

> dynamic typing is a way to defer until runtime typing aspects of the program's implementation That's more of a "how", where the bit you quoted seemed to be speaking to "why", IMO.