Why Concurrency Is Hard

Re:Why Concurrency Is Hard by lmm on Tuesday November 10, 2020 @09:07PM (#25054796)

The mixing of the array access (which is another piece of language-level special-case syntax) with the properties is what makes it verbose - "normally" you could just do something like

    config.lens(tabs[2].title) set "Suspended"

Admittedly that relies on a macro, but the macro is pretty lightweight syntax sugar - if you wanted to do it in 100% vanilla code you'd need a .lens at every step and a slightly more explicit way to name the "properties", i.e.

    config.lens(_.tabs).lens(_(2)).lens(_.title) set "Suspended"

> is it possible at least to pack it into a generic function and apply it to most/all assignments?

I don't quite understand? You can certainly write generic functions that work for any lens whose "target" is a given type.

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Re:Why Concurrency Is Hard by nyanpasu64 on Wednesday November 11, 2020 @01:10AM (#25055955)

I've heard about lenses, but never actually worked with them. This syntax seems to construct a "path" of sorts from the root to a field. What language is this? What type does the `set` operator/keyword return?

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Re:Why Concurrency Is Hard by lmm on Wednesday November 11, 2020 @02:13AM (#25056183)

It's Scala with Monocle (and it's off the top of my head, so apologies for any mistake). `set` usually returns a function for transforming values of the root type, but this simplified syntax will apply it immediately to `config`, so it'll return a copy of config with the modification applied to it.

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