kccqzy on Announcing Building Git

Comment on Announcing Building Git parent

Ruby has blocks. Python does not. And Ruby blocks are very extensively used.

blocks are the same as passing a function or a lambda in python:

    [1, 2, 3].map { |i| i + 1 }

    [i + 1 for i in [1, 2, 3]]

    def plus(i):
      return i + 1

    map(plus, [1, 2, 3])

    map(lambda i: i + 1, [1, 2, 3])

kccqzy 7y

Far from it. Ruby blocks aren't really lambdas or anonymous functions. For example when you use return inside a block, it's not just the code in the block is being returned, but the whole enclosing function. And, you don't really "call" a block but yield to it. It's not even an object that you can inspect. It's syntax. It's really a new kind of control structure. Ruby blocks have few equivalents in other languages.

localhostdotdev 7y

   def f(&block)
     block.class
   end

   f { } # => Proc
   f(&-> { }) # => Proc
   f(&lambda { }) # => Proc
   f(&:something) # => Proc

   lambda { }.class # => Proc (I think you get the idea)

   method(:f).class # => Method

   lambda { |i| i + 1 }.call(10) # => 11

you don't typically return in a block, there is implicit return. you would do "next" or "break" depending on what you want to achieve. as far as I know that's the main difference between procs and methods.

(not that anybody would do what I do, most people just use blocks, some people use yield, few people use the &block argument, but that's exactly the same)

ptx 7y

Sound a lot like inlined lambdas in Kotlin. Lambdas can be passed with the same block-like syntax, and when they're marked as "inline" you can return from the enclosing function from within the lambda (because the lambda will have its body inlined by the compiler).

Comments