Ruby Blocks

> The value 5 having a method, and that method being an iterator for its value, is kinda weird in any design sense and doesn’t seem to fix any architectural order you might expect, it’s just there because the “hack” results in pretty text when used.

I don't think this is particularly weird, in Ruby at least. The language follows object orientation to its natural conclusion, which is that everything is an object, always. There is no such thing as "just data" in Ruby, because everything is an object. Even things that would just be an `int` in most other languages are actually objects, and so they have methods. The `times` method exists on the Integer classes because doing something exactly an integer number of times happens a lot in practice.

Blocks are fundamentally different from functions due to the control flow: `return` inside a block will return the outer method, not the block. `break` stops the whole method that was invoked.

This adds some complexity in the language, but it means that it’s far more expressive. In Ruby you can with nothing but Array#each write idiomatic code which reads very similar to other traditional languages with loops and statements.

The "aesthetically pleasing" aspect of blocks is not mutually exclusive with real, first-class functions! Ruby is really more functional than that. Ruby has both lambas and method objects (pulled from instances). For example, you can write:

  let isLarge = a => a>100;

  is_large = ->(a) { a > 100 }
  is_large.call(1000)
  # => true
  is_large.(1000)
  # => true

Additionally, you can even take a reference to a method off of an object, and pass them around as though they are a callable lambda/block:

  class Foo
    def bar = 'baz'
  end

  foo_instance = Foo.new
  callable_bar = foo_instance.method(:bar)
  callable_bar.call
  # => 'baz'

  class UpcaseCertainLetters
    def initialize(letters_to_upcase)
      @letters_to_upcase = letters_to_upcase
    end

    def format(str)
      str.chars.map do |char| 
        @letters_to_upcase.include?(char) ? char.upcase : char
      end.join
    end
  end

  upcase_vowels = UpcaseCertainLetters.new("aeiuo").method(:format)
  ['foo', 'bar', 'baz'].map(&upcase_vowels)
  # => ['fOO', 'bAr', 'bAz']

  (0..10).map(&:even?)
  # => [true, false, true, false, true, false, true, false, true, false, true]

  is_div_five = ->(num) { num % 5 == 0 }
  (0..10).map(&is_div_five)
  # => [true, false, false, false, false, true, false, false, false, false, true]

If you are familiar with a true object-oriented language like Smalltalk (rather than the watered-down form of OO in C++, Java, etc.), an integer like 5 having methods makes sense because it (like everything else) is an object. Objects in Ruby aren't just window dressing -- they are its core.

Have a look at Smalltalk blocks, or FP languages, to see where Ruby's inspiration comes from.

Take a look at Kotlin, it perfected this idea

I discovered Ruby (through Rails) about twenty years ago on the dot. Coming from Perl and PHP it took me a while, but I remember the moment when I had the same realisation you did.

I still love this language to bits, and it was fun to relive that moment vicariously through someone elses eyes. Thanks for writing it up!

Assuming that by lambda you mean "an anonymous function"[1], for most intents and purposes they are, except their returns are non-local whereas functions usually have local returns.

However blocks are special forms of the language, unless reified to procs they can only be passed as parameter (not returned), and a method can only take one block. They also have some oddities in how they interact with parameters (unless reified to lambda procs).

[1] because Ruby has something called "lambda procs"

They are closures. But Ruby can do interesting and slightly reckless things, like transplanting a closure into a different evaluation scope. It’s very powerful, and also very dangerous in the wrong hands.

My understanding is that the 'extra thing' is control flow - blocks can force a return in their calling scope. For example a loop that calls a block may be terminated/skipped by a break/continue statement in the block itself. However I'm not a Ruby programmer, so please check my working.

I think Ruby teaches a sense of style, but I'm not sure that style carries over to other languages. Python was my primary language for 12 years but I'm disappointed in the depth of Knowledge python Devs have. Most barely understand the language or try to. Ruby seems to coax people into coding into a ruby way. I like that.