Show HN: Elixir/Unix style pipe operations in Ruby

5 points by bonquesha99 7 years ago · 4 comments

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pmontra 7 years ago

I quote one of the examples

    "https://api.github.com/repos/ruby/ruby".pipe do
      URI.parse
      Net::HTTP.get
      JSON.parse.fetch("stargazers_count")
      yield_self { |n| "Ruby has #{n} stars" }
      Kernel.puts
    end
    #=> Ruby has 15115 stars

Not having to type the |> like in Elixir is two shift keys less, which is good. I'm not sure about readability, because one has to spot the .pipe at the beginning of the block, but it shouldn't be a problem.

Now, if we only had pattern matching with the exact syntax of Elixir and not some monstrosity I saw around in proposals and other languages...

bonquesha99OP 7 years ago
Thanks for your feedback!
Check out this other proof of concept demonstrating ES6 style object destructuring in Ruby:
https://github.com/lendingHome/destruct
I think this same type of concept could be applied to port Elixir style pattern matching as well e.g.
```
    data = {
      name: "John Smith",
      age: 35,
      prefs: {
        lang: "en",
        tz: "UTC",
      }
    }
    
    User = Pattern { name age prefs[lang] }
    
    user = User =~ data
    user.name
    user.age
    user.lang
    
    [data].map(&User)
    
    case object
    when Pattern { some attrs[:nested][real][deep, fields] }
      Pattern!.some
      Pattern!.real
      Pattern!.deep
      Pattern!.fields
      Pattern!.nested #=> NoMethodError
    end
    
    # or define "locals" by defining temporary methods on
    # the block receiver when the "then" block is evaluated
    case object
    when Pattern { some nested[data] }.then do
      puts some
      puts data
    end
```
- pmontra 7 years ago
  Thanks. Destructuring is nice and I'll check your link.
  I'm using Elixir's pattern matching also in function definitions, to do without ifs and switches. A trivial example with Elixir syntax (hopefully correct).
  def div(a, 0), do: {:error, "can't divide by 0"} def div(a, 1), do: {:ok, a} def div(0, b), do: {:ok, 0} def div(a, b), do: {:ok, a/b}
  I'd like to have a pattern matching like that in Ruby as well. A more real world example:
  def something(%{"a" => %{"b" => b, "c" => c}}), do {:ok, b + c} def something(_), do {:error, "a didn't contain b and c"}
  Much more readable than having to write ifs inside the function/method.
  All considered, I find Ruby a more pleasant language than Elixir because of syntax, verbosity, state keeping (probably unfair, because OO is made for that vs GenServers), deployment story. I'd like to keep using it for applications that can scale by adding processes, but pattern matching is a killer feature.
  Pipelines are important in Elixir because it's functional. It would be a pain to code without them. Object oriented languages can somewhat pipeline by calling methods on results of previous methods, provided a consistent design of classes (each.map.uniq.sort). It seems that in Ruby it could remove lots of useless variables. A lot less head scratching to find sensible variable names, faster programming. I hope it gets into the language or that this gem gets popular.
  - bonquesha99OP 7 years ago
    
    Thanks! Agreed it feels like a good fit for Ruby as well!
    RE the pattern matching stuff I think the destructuring concept could be applied to look something like:
    def div(*args) case args when Pattern{[a, 0]} then [:error, "can't divide by 0"] when Pattern{[a, 1]} then [:ok, Pattern.last.a] when Pattern{[0, b]} then [:ok, 0] when Pattern{[a, b]} then [:ok, Pattern.last.a / Pattern.last.b] end end def something(object) case object when Pattern{a[b, c]} then [:ok, Pattern.last.b + Pattern.last.c] else [:error, "a didn't contain b and c"] end end
    Some shorthand to access `Pattern.last` e.g. "$~" for regex would make things even nicer!

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