Monday Learnings

I learned some cool things today, which I’d like to share here.

1) The each_cons method. It’s great. While working on Project Euler #11 with a friend, he showed me this method. It is applied to an array and takes an argument for n elements – it then returns an enumerator with the different variations of 3 consecutive elements from the array. I’m not sure I’m doing it justice, so here is an example:

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array = [1,2,3,4,5,6,7,8]
array.each_cons(3).to_a 3 # => [[1, 2, 3], [2, 3, 4], [3, 4, 5], [4, 5, 6], [5, 6, 7], [6, 7, 8]]

This was very helpful in finding the products of each possible set of four consecutive elements (horizontally) in the problem’s grid. Nice.

2)Editing a Method in Pry. Very helpful. Say you’ve defined a method in pry:

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def hello
  puts "Hello"
end

If you type edit hello in pry after this, it will open up a text editor for you to modify the method. As soon as you close and save the document, it will reload the method in pry for you to play with.

3) Using the ampersand to turn a method symbol into a proc. Check it out:

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["head", "shoulders", "knees", "toes"].collect {|word| word.reverse}
#=> ["daeh", "sredluohs", "seenk", "seot"]

Is the same as doing:

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["head", "shoulders", "knees", "toes"].collect(&:reverse)
#=> ["daeh", "sredluohs", "seenk", "seot"]

This is because the ampersand converts a symbol object to a proc for use with enumerable methods.

Small wins. That’s what it’s all about.