Convert a binary number, represented as a string (e.g. '101010'), to its decimal equivalent using first principles.
Implement binary to decimal conversion. Given a binary input string, your program should produce a decimal output. The program should handle invalid inputs.
Decimal is a base-10 system.
A number 23 in base 10 notation can be understood as a linear combination of powers of 10:
So: 23 => 2*10^1 + 3*10^0 => 2*10 + 3*1 = 23 base 10
Binary is similar, but uses powers of 2 rather than powers of 10.
So: 101 => 1*2^2 + 0*2^1 + 1*2^0 => 1*4 + 0*2 + 1*1 => 4 + 1 => 5 base 10
.
For installation and learning resources, refer to the exercism help page.
For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:
gem install minitest
If you would like color output, you can require 'minitest/pride'
in
the test file, or note the alternative instruction, below, for running
the test file.
Run the tests from the exercise directory using the following command:
ruby binary_test.rb
To include color from the command line:
ruby -r minitest/pride binary_test.rb
All of Computer Science http://www.wolframalpha.com/input/?i=binary&a=*C.binary-_*MathWorld-
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
require 'minitest/autorun'
require_relative 'binary'
# Common test data version: 1.0.0 969717d
class BinaryTest < Minitest::Test
def test_binary_0_is_decimal_0
# skip
assert_equal 0, Binary.to_decimal('0')
end
def test_binary_1_is_decimal_1
skip
assert_equal 1, Binary.to_decimal('1')
end
def test_binary_10_is_decimal_2
skip
assert_equal 2, Binary.to_decimal('10')
end
def test_binary_11_is_decimal_3
skip
assert_equal 3, Binary.to_decimal('11')
end
def test_binary_100_is_decimal_4
skip
assert_equal 4, Binary.to_decimal('100')
end
def test_binary_1001_is_decimal_9
skip
assert_equal 9, Binary.to_decimal('1001')
end
def test_binary_11010_is_decimal_26
skip
assert_equal 26, Binary.to_decimal('11010')
end
def test_binary_10001101000_is_decimal_1128
skip
assert_equal 1128, Binary.to_decimal('10001101000')
end
def test_binary_ignores_leading_zeros
skip
assert_equal 31, Binary.to_decimal('000011111')
end
def test_2_is_not_a_valid_binary_digit
skip
assert_raises(ArgumentError) { Binary.to_decimal('2') }
end
def test_a_number_containing_a_non_binary_digit_is_invalid
skip
assert_raises(ArgumentError) { Binary.to_decimal('01201') }
end
def test_a_number_with_trailing_non_binary_characters_is_invalid
skip
assert_raises(ArgumentError) { Binary.to_decimal('10nope') }
end
def test_a_number_with_leading_non_binary_characters_is_invalid
skip
assert_raises(ArgumentError) { Binary.to_decimal('nope10') }
end
def test_a_number_with_internal_non_binary_characters_is_invalid
skip
assert_raises(ArgumentError) { Binary.to_decimal('10nope10') }
end
def test_a_number_and_a_word_whitespace_spearated_is_invalid
skip
assert_raises(ArgumentError) { Binary.to_decimal('001 nope') }
end
# Problems in exercism evolve over time, as we find better ways to ask
# questions.
# The version number refers to the version of the problem you solved,
# not your solution.
#
# Define a constant named VERSION inside of the top level BookKeeping
# module, which may be placed near the end of your file.
#
# In your file, it will look like this:
#
# module BookKeeping
# VERSION = 1 # Where the version number matches the one in the test.
# end
#
# If you are curious, read more about constants on RubyDoc:
# http://ruby-doc.org/docs/ruby-doc-bundle/UsersGuide/rg/constants.html
def test_bookkeeping
skip
assert_equal 3, BookKeeping::VERSION
end
end
# works for bases from 2 to 36
module BaseN
def initialize(string)
unless self.class.valid? string
fail ArgumentError, "#{ string }:#{ string.class } is not a string representaiton of a base-#{ self.class.base } number"
end
@string = string
end
def to_decimal
digits = @string.chars.map { |char| self.class.valid_characters.index(char) }
digits.reverse.each_with_index.inject(0) do |sum, (n, i)|
sum += n * self.class.base**i
end
end
def self.included(host_class)
host_class.extend(BaseNClassMethods)
end
module BaseNClassMethods
def valid?(string)
string.chars.all? { |char| valid_characters.include? char }
end
def valid_characters
[*'0'..'9', *'A'..'Z'][0...base]
end
end
end
class Binary
include BaseN
VERSION = 1
def self.base
2
end
end
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