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lujanfernaud's solution

to Wordy in the Ruby Track

Published at Mar 10 2019 · 0 comments
Instructions
Test suite
Solution

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

Iteration 1 — Addition

Add two numbers together.

What is 5 plus 13?

Evaluates to 18.

Handle large numbers and negative numbers.

Iteration 2 — 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 — 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 — Exponentials

If you'd like, handle exponentials.

What is 2 raised to the 5th power?

32


For installation and learning resources, refer to the Ruby resources 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: 1.2.0 86d0069
class WordyTest < Minitest::Test
  def test_addition
    # skip
    problem = WordProblem.new("What is 1 plus 1?")
    assert_equal(2, problem.answer)
  end

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  def test_non_math_question
    skip
    problem = WordProblem.new("Who is the President of the United States?")
    assert_raises(ArgumentError) do
      problem.answer
    end
  end
end

wordy.rb

require "./question_parser"
require "./operation_evaluator"

class WordProblem
  OPERATION = /\d.+?\d/

  def initialize(question)
    @question = question
  end

  def answer
    raise ArgumentError, "Unknown operation" unless question.match(OPERATION)

    evaluate_problem
  end

  private

  def evaluate_problem
    values = QuestionParser.run(question)

    OperationEvaluator.run(values)
  end

  attr_reader :question
end

question_parser.rb

class QuestionParser
  OPERATORS = {
    "plus"       => "+",
    "minus"      => "-",
    "multiplied" => "*",
    "divided"    => "/"
  }.freeze

  def self.run(question)
    new(question).parse
  end

  def initialize(question)
    @question = question
  end

  def parse
    prepare_question
    parse_values
  end

  private

  def prepare_question
    @question = question.sub("What is ", "").gsub("by", "").chop.split(" ")
  end

  def parse_values
    question.map do |value|
      if OPERATORS.include?(value)
        OPERATORS[value].to_sym
      else
        value.to_i
      end
    end
  end

  attr_reader :question
end

operation_evaluator.rb

class OperationEvaluator
  def self.run(values)
    new(values).evaluate
  end

  def initialize(values)
    @values = values
    @result = 0
  end

  def evaluate
    until values.empty?
      first_item, second_item, third_item = values.slice!(0..2)

      result = if third_item
                 first_item.send(second_item, third_item)
               else
                 result.send(first_item, second_item)
               end
    end

    result
  end

  private

  attr_accessor :values, :result
end

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