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muriloime's solution

to Wordy in the Ruby Track

Published at Jun 27 2020 · 0 comments
Instructions
Test suite
Solution

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 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``````
``````class WordProblem
OPERATIONS = { 'What is ' => '',
'?' => '',
'plus' => :+,
'minus' => :-,
'multiplied by' => :*,
'divided by' => :/ }.freeze

def initialize(question)
@question = question.gsub(Regexp.union(OPERATIONS.keys), OPERATIONS)
end

def eval_binary_expression(operand1, operator, operand2)
operand1.send(operator, operand2)
end

def operands
@question.scan(%r{[\d\+\-\*/]+})
end

def answer
raise ArgumentError if /[a-zA-Z]/.match?(@question)

initial_value, *tail_values = operands

tail_values.each_slice(2)
.inject(initial_value.to_i) do |accumulator, (operator, operand)|
eval_binary_expression(accumulator, operator, operand.to_i)
end
end
end``````

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