#parallel assignment

Working on the Ruby Koans, I encountered these simple assignments as part of a test:

array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] sum = 0

I was really excited to realize I could simply use parallel assignment and do the same thing in one fell swoop:

sum, *array = (0..10).to_a

Today we began to build a chess game. Anyone who knows me, knows that I'm nuts for chess. I'm enjoying this assignment a bunch. My partner Mark and I really wanted to make the code modular and well-organized. The past two days, we haven't been learning new concepts so much as honing our programming style. Assignments like Minesweeper and Chess really force us to consider how domain objects relate to each other, and it gives us great practice in decomposing methods and grouping inherited functionality.

Learned a cool trick with parallel assignment today: you can define multiple variables on a single line to point to multiple items in an array.

diapers = ["huggies","pampers"] my_diaper, your_diaper = diapers

In the snippet above, I'd be wearing huggies, and you pampers.

Another great thing to do is to overwrite the [ ] method when constantly dealing with multi-dimensional arrays.

def [ ] (position)   self[position[0]][position[1]] end

Now instead of asking for a position by querying two nested arrays, you can just pass in a single array and let the [ ] function take care of separating your request and delegating it to the sub arrays.

You'd pass it like this.

location_of_my_pacifier = [["SF", "CA"], ["SOMA", "160 Folsom"]]

pacifier_thief = Thief.new(location = ["SF", "160 Folsom"])

puts "Run away! Don't take my binkie!" if pacifier_thief.location == pacifier[location_of_my_pacifier]

Let assume that you transform a hash

{ :a => 1, :b => 2 }

into local variables somewhere in your code and forget to remove a little comma after one line

a = 1, b = 2

You still have a valid ruby code but it produces something unexpected!

a # => [1,2] b # => 2

Why? Because of the comma ruby uses multiple assignment operator to assign values. Let write the code into one line to clarify what happens here.

a = 1, b = 2 a = 1, (b = 2) a = 1, 2 a # => [1,2]