rdnetto · HackerTrans

hace 8 añosdiscuss

Programming languages having rigid syntax is like English being limited to the Latin alphabet - the opportunities for creativity lie in the combinations of higher level structures.

rdnetto

hace 8 añosdiscuss

This is standard practice where I work due to SOX compliance. (No pushing directly to master, all PRs need at least one other person's approval). In practice it's not an issue, since PRs are good practice anyway.

rdnetto

hace 8 añosdiscuss

You know that OSX and Linux both use the same printer stack (CUPS) right?

rdnetto

hace 9 añosdiscuss

> C++ cannot be covered by package management in the same way interpreted languages are. The problem space is vastly more complex. It starts with optional language features that often get get disabled in projects (most often RTTI and exceptions), continues with incompatible ABIs between compilers and even compiler revisions and does not stop with the presence of sometimes countless compiler flags for optional features and dependencies.

Haskell has most of the same problems and Stack handles them easily. Each source file in a project can use different language extensions, all transitive dependencies are compiled from source, and there's even CI to re run tests whenever a package is bumped.

rdnetto

hace 9 añosdiscuss

A variation on this would be to put the database behind a service that abstracted over the schema, though that only works for basic CRUD queries and not complex aggregations. This service would probably evolve from the monolith.

rdnetto

hace 9 añosdiscuss

You can do that in Python by converting the list to a tuple before passing it in. The need for a defensive copy is unavoidable as long as you're using mutable data types though.

rdnetto

hace 9 añosdiscuss

You probably want to compress it as well - that can easily reduce the file size by an order of magnitude.

rdnetto

hace 9 añosdiscuss

Would be really great to see this make it's way into the language. Here are some ways I've found to work around its absence: * adding a match() function to a common base type. So if it could have subtypes Foo(x), Bar(y, z), then the signature would look like:

  <T> T match(Function<X, T> foo, BiFunction<Y, Z, T> bar);

* in the cases where I don't have control over the common base type, I've written a builder pattern that constructs a sequence of predicate-function pairs and applies them appropriately. This looks like so:

    new PatternMatchingHelper()
    .append(Foo.class, foo -> doSomething(foo.x))
    .append(Bar.class, bar -> doSomethingElse(bar.y, bar.z))
    .otherwise(x -> fallbackValue())
    .apply(objectOfUnknownType);

The main disadvantage here is that it doesn't work well with generics, because the class objects have raw types.

You could probably extend the second approach to get something close to the arbitrary predicates that pattern matching would provide, but the syntax wouldn't be nearly a clean as having it in the language.

rdnetto

hace 9 añosdiscuss

I suspect the third function is the one for running the monad. It's different for each one, so it's not part of the type class, but you do need it to use a given monad. (Except IO, though even it has unsafePerformIO)

rdnetto

hace 9 añosdiscuss

I used it for a while, ended up switching to Haskell, which had a lot of similar benefits despite being so different.

If you're going to use it, I highly recommend the D Programming Language (book). It's extremely well written, and remains once of my favourite technical books.

rdnetto

hace 9 añosdiscuss

It's worth noting you can implement something similar in OOP languages using Church encoding: http://blog.higher-order.com/blog/2009/08/21/structural-patt...

rdnetto

hace 9 añosdiscuss

> I can almost guarantee that code was not written by an inexperienced or low skill coder. > If it was, you'd have a large complex function that took large complex state as its input, and probably maintained some kind of hidden internal state in some kind of async deferred loop after it returned or some combination of the above. > Have you worked with inexperienced FP programmers? > It's not fun.

No pure FP language will allow you to do that without the function's type signature reflecting that - it would need to return its value in some kind of state/async monad.

Now, if you're talking about FP in a traditionally OOP language, then I agree with you, but that's an apples to oranges comparison.

> Inexperienced OOP is a lot easier to deal with, because the entity level API validation is all you care about; you don't care about how hideously the internals were implemented as long as the tests pass. There can be any number of bugs and spaghetti inside the object, but you don't care, because you don't see it (until it manifests as bugs; but then you just add more tests and make them go away until all the tests pass).

This approach doesn't work for things that are difficult to test. e.g. you can only ensure your types are thread safe by reasoning about their use of locks, volatile, etc., because any attempt to test this is dependent on the implementation details of your runtime (e.g. the JVM) and the amount of load its under. Best case you get a flaky test, worst case you miss a bug that blows up in production.

But this is a tangent, because TDD is not specific to OOP - it works just as well with FP.

> but the point here is that someone has to define the module level interface, and how it behaves as a state machine (regardless of if the state comes in 'pure' and is passed around or is encapsulated internally); and that's OOP, not an inheritance hierarchy.

Pure state is an oxymoron. The idea is not that you pass a mutable argument in, but that you don't have the ability to mutate data at all. At best, you can return some instructions on how to mutate (e.g. the state monad), but its the consumer of your code who decides what to do with that, which prevents you from hiding side-effects, and simplifies testing.

Defining a module level interface and behaviour is just API design, not OOP.

rdnetto

hace 9 añosdiscuss

A counter-point to this is that OOP languages lack support for ad-hoc polymorphism. i.e. the ability for third-party code to define an implementation of an interface for a pre-existing type. The two approaches used to work around this are the adapter pattern, and explicitly taking an object implementing the desired behaviour as a second argument (e.g. Comparators in Java).

In contrast, most (typed) FP languages support typeclasses / traits, which makes a lot of code considerably simpler.

rdnetto

hace 9 añosdiscuss

I have the same toaster and it is awesome. My favourite feature is that its Frozen button works perfectly, which is great if you don't have bread that often.

rdnetto

hace 9 añosdiscuss

IIRC, Panasonic owns the patent on inverters, but they definitely make a microwave with a simple knob interface, because I have one (http://www.panasonic.com/au/consumer/household/microwave-ove...)

rdnetto

hace 9 añosdiscuss

That's not a bad answer though - it demonstrates you understand the value of those things we should have had years ago, and might include things which aren't being worked on yet (even though they should be).

rdnetto

hace 10 añosdiscuss

Haskell and Scala are pretty awesome at embedded DSLs, because of do-blocks. You can use them to bind some value to a symbol (i.e. assign a variable) inside the eDSL, which isn't possible in most languages. (Contrast this to, say, eDSLs in Java, which are limited to fancy builder patterns).

rdnetto

hace 10 añosdiscuss

> I think you are confusing type errors with modeling errors, but that's very common.

How would you distinguish between them? Strong/expressive type systems encode the modelling in a way which is mechanically verifiable. e.g. by not permitting negative or fractional numbers to be submitted to a function which indexes an array.

rdnetto

hace 10 añosdiscuss

> Static typing helps a lot to catch basic type errors but it is surely not the "Messiah" of code safety.

I'd argue that type safety is only one benefit of strong types - the others being better documentation[1] and a design which is clearer and easier to reason about.[2] You can get both in a dynamically typed language, but they're much less common since the compiler doesn't require them.

[1] I've lost count of how many times I've looked at some function in Python or Javascript and had no idea what kind of values I was supposed to provide.

[2] My go-to example of this is how in Persistent (a Haskell ORM), values which have been inserted into the database (entities) and which have not have different types, since the non-inserted values don't know what their primary key is yet. This makes it much easier to reason about where the values are coming from and what needs to be done with them.

> Stack works only because it is an isolated repository where the maintainers have to take a lot of attention to make sure that new code doesn't break other code.

In practice, the only breakage checked for is compilation errors. The onus is still on library authors to declare compatibility bounds in their cabal files, which is why [PVP](http://pvp.haskell.org/) is still a thing.

I'm also not sure how accurate it is to call it isolated - it's pretty much at the centre of the ecosystem at this point.

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