ADT through the looking glass – lenses, prisms and other optics in Scala

I find the Monocle library does a good job of describing the motivation for type optics: <a href="http:&#x2F;&#x2F;julien-truffaut.github.io&#x2F;Monocle&#x2F;" rel="nofollow">http:&#x2F;&#x2F;julien-truffaut.github.io&#x2F;Monocle&#x2F;</a><p>Where I&#x27;ve used this in real code is via circe-optics (json parsing). An example: <a href="https:&#x2F;&#x2F;stackoverflow.com&#x2F;questions&#x2F;36724068&#x2F;how-to-parse-a-json-scala-without-case-classes" rel="nofollow">https:&#x2F;&#x2F;stackoverflow.com&#x2F;questions&#x2F;36724068&#x2F;how-to-parse-a-...</a>

I mainly program in low-level imperative languages (mostly C&#x2F;C++), and occasionally dabbled in some functional languages (like Ocaml and Elm). But I don’t really understand why you would need such a convoluted system to get&#x2F;mutate some values in a data structure in Scala. Doesn’t Scala allow mutability throughout its language already (unlike Haskell)?

Monocle also ships with the macro annotation <i>monocle.macros.Lenses</i> that cuts out even more of the boilerplate and works with intellij&#x27;s autocomplete<p><pre><code> import monocle.macros.Lenses @Lenses case class Foo(bar: Int) val x = Foo(1) assert(Foo.bar.get(x) == 1)</code></pre>

<a href="https:&#x2F;&#x2F;arxiv.org&#x2F;abs&#x2F;1809.00738" rel="nofollow">https:&#x2F;&#x2F;arxiv.org&#x2F;abs&#x2F;1809.00738</a> is really nice for general context. Plus can implement some of these generalizations from what is already here.

I like working in Scala quite a bit, but always wince at the &quot;instead of using threading primitives consider this 10x more exotic immutable approach&quot; lead-in. Does anyone here really work that way?

Takes a long time to parse because it the text has a lot of typos.