Scalafix VS bytestring

I also recommend using Scalafix. It's a tool which can lint your codebase, checking for potentially problematic things, like

Scalafix

scala-fix seems relevant for the /= removal problem.

or `NonUnitStatements` without explicit annotation.

This effectively locks you into writing pure code (you can extend the linter to cover other things like not using `Future` or not using Java libs outside of `MonadError` from cats[4]). The linters operate on typed ASTs at compile time, and have plugins for the most popular scala build tools. Coupled with `-XFatalWarnings', you can guarantee that nothing unexpected happens unless you explicitly pop the escape hatch, for the most part.

You can still bring in external libraries that haven't been compiled with these safties in place, so you aren't completely safe, but if you use ZIO[5]/Typelevel[6] libraries you can be reasonably assured of referentially transparent code in practice.

There are three schools of thought, roughly, in the scala community towards the depth of using the type system and linters to provide guarantees and capabilities, currently:

1) Don't attempt to do this, it makes the barrier to entry to high for Scala juniors. I don't understand this argument - you want to allow runtime footguns you could easily prevent at compile time because the verifiable techniques take time to learn? Why did you even choose to use a typesafe language and pay the compilation time penalty that comes with it?

2) Abstract everything to the smallest possible dependency interface, including effects (code to an effect runtime, F[_] that implements the methods your code needs to run - if you handle errors, F implements MonadError, if you output do concurrent things, F implements Concurrent, etc.) and you extend the effect with your own services using tagless final or free.

3) You still use effect wrappers, but you bind the whole project always to use a concrete effect type, avoiding event abstraction, thus making it easier to code, and limiting footguns to a very particular subset (mainly threadpool providers and unsafeRun or equivalent being called eagerly in the internals of applications).

My opinion is that smallest interface with effect guarantees (#2) is best for very large, long maintenance window apps where thechoice of effect runtime might change(app), or is out of the devs' control (lib); and #3 is best for small apps.

TL/DR; You can go a really, really long way to guaranteeing effects don't run in user code in scala. Not all the way like Haskell, but far enough that it's painful to code without conforming to referential transparency.

1. https://github.com/scalacenter/scalafix

2. https://github.com/scalaz/scalazzi

3. http://www.wartremover.org/

4. https://typelevel.org/cats/api/cats/MonadError.html

5. https://zio.dev/

6. https://typelevel.org/

I actually still recommend using WartRemover, at least until there's an equivalent ScalaFix ruleset that's as effective.

Probably linting rules defined in Scalafix. See https://github.com/scalacenter/scalafix/blob/master/scalafix-rules/src/main/scala/scalafix/internal/rule/DisableSyntax.scala#L11 for an example.

The documentation is itself fairly funny, for those who don’t care to click ahead:

> This "function" has a superficial similarity to ‘unsafePerformIO’ but it is in fact a malevolent agent of chaos. It unpicks the seams of reality (and the IO monad) so that the normal rules no longer apply. It lulls you into thinking it is reasonable, but when you are not looking it stabs you in the back and aliases all of your mutable buffers. The carcass of many a seasoned Haskell programmer lie strewn at its feet.

> Witness the trail of destruction:

    https://github.com/haskell/bytestring/commit/71c4b438c675aa360c79d79acc9a491e7bbc26e7

If you bring in efficient strings from bytestring, densely packed arrays from vector, and an in-place sort from vector-algorithms, you can bring it down to 275ms (uses 19MB of mem).

bytestring

Note that this release is broken for Windows.

I've opened https://github.com/haskell/bytestring/issues/455 so the situation can be improved. You're very welcome to chime in on the discussion or to contribute some of the missing documentation yourself! :)

Highlights from the changelog:

Well, ByteString in particular should not have an IsString instance in a new report. That's pretty clear by https://github.com/haskell/bytestring/issues/140 : the concensus is that there is no good solution right now, but it should not have gotten an IsString instance in the first place. If a theoretical new Haskell Report 202x includes OverloadedStrings (as it should) to handle string literals analogously to numeric literals, I'd expect it to not give ByteString (which is really just a collection of octets) an IsString instance, with all it's issues and rattail due to the encoding question being implicitized.

Standard streaming libraries. They are being written by people that make the effort to understand performance and I have a hope that they make sure their streams run in linear space under any optimizations. It is curious and unsettling that we have standard lazy text and byte streams at the same time — and the default lazy lists, of course. I have been doing some work on byte streams and what I found out is that there is no way to check that your folds are actually space constant even if the value in question is a primitive, like say a byte — thunks may explode and then collapse over the run time of a single computation, defying any effort at inspection.