Add ruby binary assignment

assignments/ruby/binary/data.yml

@@ -0,0 +1,4 @@
+---
+blurb: "Write a program that will convert a binary number, represented as a string (i.e. '101010'), to it's decimal equivalent using first principles"
+source: "All of Computer Science"
+source_url: "http://www.wolfram-alpha.com"

assignments/ruby/binary/details.md

@@ -0,0 +1,23 @@
+You may not use built-in ruby libraries or gems to accomplish the conversion.
+
+The program should consider strings specifying an invalid binary as the value 0.
+
+This is how computers work:
+
+```bash
+# "1011001"
+  1     0     1     1     0     0     1
+2^6 + 2^5 + 2^4 + 2^3 + 2^2 + 2^1 + 2^0
+ 64 +   0 +  16 +   8 +   0 +   0 +   1 = 89
+```
+
+If you want to write extra tests and/or check your answers, feel free to use irb:
+
+```ruby
+irb(main):001:0> 0b1011001
+=> 89
+irb(main):002:0> 0b1101
+=> 13
+irb(main):003:0> 0b110110110110101
+=> 28085
+```

assignments/ruby/binary/example.rb

@@ -0,0 +1,15 @@
+class Binary
+
+  attr_reader :digits
+  def initialize(decimal)
+    @digits = decimal.reverse.chars.collect(&:to_i)
+  end
+
+  def to_decimal
+    decimal = 0
+    digits.each_with_index do |digit, index|
+      decimal += digit * 2**index
+    end
+    decimal
+  end
+end

assignments/ruby/binary/test.rb

@@ -0,0 +1,44 @@
+require 'minitest/autorun'
+require 'minitest/pride'
+require_relative 'binary'
+
+class BinaryTest < MiniTest::Unit::TestCase
+  def test_binary_1_is_decimal_1
+    assert_equal 1, Binary.new("1").to_decimal
+  end
+
+  def test_binary_10_is_decimal_2
+    skip
+    assert_equal 2, Binary.new("10").to_decimal
+  end
+
+  def test_binary_11_is_decimal_3
+    skip
+    assert_equal 3, Binary.new("11").to_decimal
+  end
+
+  def test_binary_100_is_decimal_4
+    skip
+    assert_equal 4, Binary.new("100").to_decimal
+  end
+
+  def test_binary_1001_is_decimal_9
+    skip
+    assert_equal 9, Binary.new("1001").to_decimal
+  end
+
+  def test_binary_11010_is_decimal_26
+    skip
+    assert_equal 26, Binary.new("11010").to_decimal
+  end
+
+  def test_binary_10001101000_is_decimal_1128
+    skip
+    assert_equal 1128, Binary.new("10001101000").to_decimal
+  end
+
+  def test_invalid_binary_is_decimal_0
+    skip
+    assert_equal 0, Binary.new("carrot").to_decimal
+  end
+end

lib/exercism.rb

@@ -25,7 +25,7 @@ def self.current_curriculum
         bob word-count anagram beer-song nucleotide-count
         rna-transcription point-mutations phone-number
         grade-school leap etl space-age grains gigasecond
-        triangle scrabble-score roman-numerals
+        triangle scrabble-score roman-numerals binary
       )
       @curriculum.add(rb, rb_slugs)