Mastering Ruby Closures

Chapter 2

1. Here’s an implementation that uses our version of Array#each:

   class Array
     def each
       x = 0
       while x < self.length
         yield self[x]
         x += 1
       end
     end
   
     def map
       res = []
       each { |x| res << yield(x) }
       res
     end
   end

   Here, we make use of the element that is yielded from each iteration of each and collect each element into res.

2. Here’s a possible implementation:

   class String
     def each_word
       x = 0 # => 0
       words = self.split
       while x < words.length
         yield words[x]
         x += 1
       end
     end
   end

3. Your final code should look something like this:

   class File
     def self.open(name, mode, &block)
       file = new(name, mode)
       return file unless block_given?
       yield(file)

     ensure ...