7L7W Ruby - Day 2

day2_do.rb

=begin
Print the contents of an array of sixteen numbers, four numbers
at a time, using just each. 
=end

i=0
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16].each do |x| 
i=i+1
print "#{x} "
puts "" if i%4==0
end

#Now, do the same with each_slice in Enumerable.
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16].each_slice(4) {|a| p a}

=begin
The Tree class was interesting, but it did not allow you to specify
a new tree with a clean user interface. Let the initializer accept a
nested structure with hashes and arrays. You should be able to
specify a tree like this: {’grandpa’ => {’ dad’ => {’child 1’ => {}, ’child
2’ => {} }, ’uncle’ => {’child 3’ => {}, ’child 4’ => {} } } }.
=end
class Tree
	attr_accessor :children, :node_name

	def initialize(name, children=[])
		@children = children
		@node_name = name
	end

	def visit_all(&block)
		visit &block
		children.each {|c| c.visit_all &block}
	end

	def visit(&block)
		block.call self
	end
end

ruby_tree = Tree.new ("grandpa",
		[Tree.new("dad",[Tree.new("child 1"), Tree.new("child 2")]),
		Tree.new("uncle",[Tree.new("child 3"), Tree.new("child 4")])])

puts "Visiting a node"
ruby_tree.visit {|node| puts node.node_name}
puts

puts "visiting entire tree"
ruby_tree.visit_all {|node| puts node.node_name}
puts
puts
puts

class Tree2
	attr_accessor :children, :node_name

	def initialize(nested)
		@children = nested.values[0].map {|key, value| Tree2.new(Hash[key, value])}
		@node_name = nested.keys[0]
	end

	def visit_all(&block)
		visit &block
		children.each {|c| c.visit_all &block}
	end

	def visit(&block)
		block.call self
	end
end

ruby_tree2 = Tree2.new({'grandpa' => {'dad' => {'child 1' => {}, 'child 2' => {} }, 'uncle' => {'child 3' => {}, 'child 4' => {} } } })
puts "Visiting a node"
ruby_tree2.visit {|node| puts node.node_name}
puts

puts "visiting entire tree"
ruby_tree2.visit_all {|node| puts node.node_name}
puts

=begin
Write a simple grep that will print the lines of a file having any
occurrences of a phrase anywhere in that line. You will need to do
a simple regular expression match and read lines from a file. (This
is surprisingly simple in Ruby.) If you want, include line numbers.
=end

File.open("sampleFile.txt", "r") {|aFile| aFile.each_line {|line| puts "#{aFile.lineno}: #{line}" unless line.match('f.la') == nil}}

day2_find.rb

# Find out how to access files with and without code blocks.
# With out block
aFile = File.new("testfile", "r")

# ... process the file

aFile.close

# With blocks
File.open("testfile", "r") do |aFile|

# ... process the file

end

# What is the benefit of the code block?
# auto close of the file.

# How would you translate a hash to an array? 
a =  {1=> "one", 2 => [2,"two"], 3 => "three"}
a.flatten # => [1, "one", 2, [2, "two"], 3, "three"]
a.to_a # => [[1, "one"], [2, [2, "two"]], [3, "three"]]

# Can you translate arrays to hashes?
hash = [[:first_name, 'Shane'], [:last_name, 'Harvie']].inject({}) do |result, element|
  result[element.first] = element.last
  result
end # => {:first_name=>"Shane", :last_name=>"Harvie"}
hash.class # => Hash

# Next method also works, but I don't know why
a = Hash[*[[:first_name, 'Shane'], [:last_name, 'Harvie']].flatten] # => {:first_name=>"Shane", :last_name=>"Harvie"}
a.class # => Hash

# For flatted arrays
a= [1, "one", 2, "two"] # => [1, "one", 2, "two"]
Hash[*a] # => {1=>"one", 2=>"two"}

# Can you iterate through a hash?
h = { "a" => 100, "b" => 200 } # => {"a"=>100, "b"=>200}
h.each {|key, value| puts "#{key} is #{value}" }
#a is 100
#b is 200
#=> {"a"=>100, "b"=>200}

# You can use Ruby arrays as stacks. What other common data structures do arrays support?
# you can treat arrays as stacks, sets, queues, dequeues, and fifos