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chandeeland's solution

to Wordy in the Ruby Track

Published at Jul 13 2018 · 1 comment
Instructions
Test suite
Solution

Note:

This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Parse and evaluate simple math word problems returning the answer as an integer.

Iteration 1 β€” Addition

Add two numbers together.

What is 5 plus 13?

Evaluates to 18.

Handle large numbers and negative numbers.

Iteration 2 β€” Subtraction, Multiplication and Division

Now, perform the other three operations.

What is 7 minus 5?

2

What is 6 multiplied by 4?

24

What is 25 divided by 5?

5

Iteration 3 β€” Multiple Operations

Handle a set of operations, in sequence.

Since these are verbal word problems, evaluate the expression from left-to-right, ignoring the typical order of operations.

What is 5 plus 13 plus 6?

24

What is 3 plus 2 multiplied by 3?

15 (i.e. not 9)

Bonus β€” Exponentials

If you'd like, handle exponentials.

What is 2 raised to the 5th power?

32


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 wordy_test.rb

To include color from the command line:

ruby -r minitest/pride wordy_test.rb

Source

Inspired by one of the generated questions in the Extreme Startup game. https://github.com/rchatley/extreme_startup

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

wordy_test.rb

require 'minitest/autorun'
require_relative 'wordy'

# Common test data version: 1.0.0 5b8ad58
class WordyTest < Minitest::Test
  def test_addition
    # skip
    question = 'What is 1 plus 1?'
    assert_equal(2, WordProblem.new(question).answer)
  end

  def test_more_addition
    skip
    question = 'What is 53 plus 2?'
    assert_equal(55, WordProblem.new(question).answer)
  end

  def test_addition_with_negative_numbers
    skip
    question = 'What is -1 plus -10?'
    assert_equal(-11, WordProblem.new(question).answer)
  end

  def test_large_addition
    skip
    question = 'What is 123 plus 45678?'
    assert_equal(45801, WordProblem.new(question).answer)
  end

  def test_subtraction
    skip
    question = 'What is 4 minus -12?'
    assert_equal(16, WordProblem.new(question).answer)
  end

  def test_multiplication
    skip
    question = 'What is -3 multiplied by 25?'
    assert_equal(-75, WordProblem.new(question).answer)
  end

  def test_division
    skip
    question = 'What is 33 divided by -3?'
    assert_equal(-11, WordProblem.new(question).answer)
  end

  def test_multiple_additions
    skip
    question = 'What is 1 plus 1 plus 1?'
    assert_equal(3, WordProblem.new(question).answer)
  end

  def test_addition_and_subtraction
    skip
    question = 'What is 1 plus 5 minus -2?'
    assert_equal(8, WordProblem.new(question).answer)
  end

  def test_multiple_subtraction
    skip
    question = 'What is 20 minus 4 minus 13?'
    assert_equal(3, WordProblem.new(question).answer)
  end

  def test_subtraction_then_addition
    skip
    question = 'What is 17 minus 6 plus 3?'
    assert_equal(14, WordProblem.new(question).answer)
  end

  def test_multiple_multiplication
    skip
    question = 'What is 2 multiplied by -2 multiplied by 3?'
    assert_equal(-12, WordProblem.new(question).answer)
  end

  def test_addition_and_multiplication
    skip
    question = 'What is -3 plus 7 multiplied by -2?'
    answer = WordProblem.new(question).answer
    message = "You should ignore order of precedence. -3 + 7 * -2 = -8, not #{answer}"
    assert_equal(-8, answer, message)
  end

  def test_multiple_division
    skip
    question = 'What is -12 divided by 2 divided by -3?'
    assert_equal(2, WordProblem.new(question).answer)
  end

  def test_unknown_operation
    skip
    question = 'What is 52 cubed?'
    assert_raises ArgumentError do
      WordProblem.new(question).answer
    end
  end

  def test_non_math_question
    skip
    question = 'Who is the President of the United States?'
    assert_raises ArgumentError do
      WordProblem.new(question).answer
    end
  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 1, BookKeeping::VERSION
  end
end
class WordProblem

  attr_reader :query

  def initialize(query)
    @query = query
  end

  def answer
    math = query.gsub(/What is/,'').gsub(/\?\z/,'').split(' ')
    a = math.shift
    while math.count > 0
      op = math.shift
      math.shift if op == 'multiplied' || op == 'divided'
      a = send(op.to_sym, a.to_i, math.shift.to_i)
    end
    a
  end

  def plus(a,b)
    a + b
  end

  def minus(a,b)
    a - b
  end

  def multiplied(a, b)
    a * b
  end

  def divided(a,b)
    a / b
  end

  def method_missing
    raise ArgumentError
  end

end

Community comments

Find this solution interesting? Ask the author a question to learn more.
Avatar of kotp

Method missing is a time bomb waiting to happen for this code, as it can hide the real problem, by raising ArgumentError when it should be raising another error instead.

The style seems to be inconsistent with argument lists, and should likely have a space after the comma in each. The "good style" is shown on line 28.

The names a and b are not descriptive, there are names for those things that are being asked for.

The names:

Addition

addends

Subtraction

minuend subtrahend

Multiplication

multiplicand multiplier

Division

dividend divisor

The argument list becomes helpful as documentation. Of course, the code is very small, and simple to go into and read. And the names make enough sense to intuit what the arguments may be, even with the names as they are.

It is just something to think about.

What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?