What do you consider to be the definition of a “de...
# thinking-togetherj
Josh Marinacci
07/21/2019, 2:12 AMWhat do you consider to be the definition of a “declarative” language? I ask because I keep running across build tools which claim to be easier/superior because they are declarative, yet without fail they run up against a wall where they keep trying to shoehorn in more features while remaining declarative, and instead should have just gone to a full Turing complete language.
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Kartik Agaram
07/21/2019, 2:50 AM
What I think of declarative build systems: https://news.ycombinator.com/item?id=15043432#15044027 (That whole thread is about my draconian solution.)
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Kartik Agaram
07/21/2019, 2:57 AM
Regarding "declarative" more broadly, I still find this thread from April memorable, about the distinction between declarative and composable: https://futureofcoding.slack.com/archives/C5T9GPWFL/p1556655545323500 (before, after and sub-thread)
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Duncan Cragg
07/21/2019, 9:37 AMJust because a lot of popular declarative languages (spreadsheets, SQL, CSS, makefiles, XSLT, etc) started off not Turing Complete doesn't mean declarative languages in general can't be! Once you add any kind of circularity over evolving state, you get TCness, and it doesn't need to make the language much more complex or hard to understand.
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Josh Marinacci
07/21/2019, 3:51 PMI like what you are saying in that thread @Kartik Agaram. As an experiment I built a simple build system that is just regular JS functions using memoization. So far it’s very easy to read and extend. It feels like having a bunch of build-centric utility functions is better than creating a new declarative language.
Josh Marinacci
07/21/2019, 3:54 PMalso, async and arrow functions make the JS surprisingly concise. If I can write a build system in a ‘declarative style’ while still using regular functions, then the need for a custom build system seems much less.
Josh Marinacci
07/21/2019, 3:55 PMAm I missing something? Why did build systems evolve towards declarative DSLs ?
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Duncan Cragg
07/21/2019, 4:03 PM? they started as declarative languages: makefiles!
Duncan Cragg
07/21/2019, 4:04 PMit's more powerful to be able to describe the "what" not the "how" of a build: to describe the end state, then hit "go", and let the algorithms decide on the necessary steps
Duncan Cragg
07/21/2019, 4:04 PMthis gives idempotency: you can say "go" whenever you like
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Kartik Agaram
07/21/2019, 4:43 PM
Yeah, it was this kind of spherical-cow theoretical thinking 😄
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makemakemake/bin/shj
Josh Marinacci
07/21/2019, 7:22 PMhere’s an example of what I’m talking about. In the early days of Java people used make files or shell scripts. At some point they started using Ant. Ant is declarative with a syntax based on XML. It worked fine, but people kept extending it to do more things as their code bases got bigger
Josh Marinacci
07/21/2019, 7:22 PMThe only way to extend ANT was to add new tasks, written in Java, but all data had to go from one section to another as strings. You would spend a lot of time thinking about how to shoe-horn what you wanted into the ANT model.
Josh Marinacci
07/21/2019, 7:23 PMEven though, by definition, you had this very powerful language, Java, which it was built in. Eventually ANT became hard to maintain so they built Maven, which grew into even more of a mess (though it did introduce the repo system which is still the only good part of Maven)
Josh Marinacci
07/21/2019, 7:24 PMToday lots of tools still run on make, or things which generate make.
Josh Marinacci
07/21/2019, 7:24 PMI think it would be an interesting experiment to use functional programming in a proper turing complete language to as a build system. Would it be more extensible and easier to understand than a make file? Maybe, maybe not.
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Garth Goldwater
07/22/2019, 2:23 PM🤦♂️peak HN galaxy brain
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Josh Marinacci
07/22/2019, 4:58 PMha hah
Josh Marinacci
07/22/2019, 4:58 PMagain HN misses the point
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wtaysom
07/24/2019, 6:26 AMHistorically, declarative answers what, imperative answers how — and beyond that a lot of context matters. At the least, we could say language/framework/library is declarative for a use if it does some part of it automatically or implicitly, which would otherwise require some tedious or tricky work.
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