# recroot89's solution

## to Wordy in the Ruby Track

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

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

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
# skip
problem = WordProblem.new("What is 1 plus 1?")
end

skip
problem = WordProblem.new("What is 53 plus 2?")
end

skip
problem = WordProblem.new("What is -1 plus -10?")
end

skip
problem = WordProblem.new("What is 123 plus 45678?")
end

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

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

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

skip
problem = WordProblem.new("What is 1 plus 1 plus 1?")
end

skip
problem = WordProblem.new("What is 1 plus 5 minus -2?")
end

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

skip
problem = WordProblem.new("What is 17 minus 6 plus 3?")
end

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

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}"
end

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

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

def test_non_math_question
skip
problem = WordProblem.new("Who is the President of the United States?")
assert_raises(ArgumentError) do
end
end
end``````
``````# frozen_string_literal: true

class WordProblem
OPERANDS = {
'plus' => '+',
'minus' => '-',
'multiplied by' => '*',
'divided by' => '/'
}.freeze

def initialize(example)
@example = example
end

unless example.start_with?('What is') && example.end_with?('?')
raise ArgumentError
end

first, *rest = example_elements
rest.each_with_index.reduce(first.to_i) do |acc, (item, index)|
next_item = rest[index + 1].to_i
case item
when '+'
acc + next_item
when '-'
acc - next_item
when '*'
acc * next_item
when '/'
acc / next_item
else
acc
end
end
end

private

def example_elements
formatted_example = example.delete_prefix('What is ').delete_suffix('?')
OPERANDS.keys.each_with_object(formatted_example) { |op, str| str.gsub!(op, OPERANDS[op]) }
raise ArgumentError if formatted_example.match?(/[a-zA-Z]+/)

formatted_example.split
end
end``````