Domain-Specific Language Pattern

Objectives

During this lab session:

Students will write and test Ruby code that implements the Domain-Specific Language (DSL) pattern.

This activity helps students develop the following skills, values and attitudes: ability to analyze and synthesize, capacity for identifying and solving problems, and efficient use of computer systems.

Activity Description

This activity can be developed individually or in pairs.

Create a folder called dsl. Inside this folder, create two files called: jankenpon.rb and jankenpon_test.rb.

All Ruby source files must start with a comment containing the lab’s title, date, and the authors’ personal information. For example:
```
# Domain-Specific Language Pattern
# Date: 30-Mar-2016
# Authors:
#          A00456654 Thursday Rubinstein 
#          A01160611 Anthony Stark
```
In the jankenpon.rb source file, implement an internal Domain-Specific Language (DSL) that allows you to see the results of a Rock-Paper-Scissors-Lizard-Spock (a.k.a. Jan-ken-pon five-weapon expansion) hand game.

The rules of this game are as follows:
- Scissors cut Paper
- Paper covers Rock
- Rock crushes Lizard
- Lizard poisons Spock
- Spock smashes Scissors
- Scissors decapitate Lizard
- Lizard eats Paper
- Paper disproves Spock
- Spock vaporizes Rock
- Rock crushes Scissors
These rules are summarized in the following image:

And this is how Sheldon Cooper explains the game on The Big Bang Theory (Season 2, episode 8, “The Lizard–Spock Expansion”):

Your DSL should support five “literal” values: Rock, Paper, Scissors, Lizard, and Spock. These values can be combined with the plus (+), minus (-) and parenthesis operators to conform complex expressions. Let A and B be expressions. The expression “A + B” returns the winner between A and B, while “A - B” returns the loser. Additionally, whenever the + and - operators execute the rule being applied is displayed on the standard output. Precedence and associativity of the operators follow Ruby’s rules.

For example, this DSL code:
```
show Spock - (Lizard + Paper)
```
should display the following:
```
Lizard eats Paper (winner Lizard)
Lizard poisons Spock (loser Spock)
Result = Spock
```
The show command is responsible for the last line of the output, showing the result of the expression it takes as input.

Notice that the result and effect of “A + B” are the same as “B + A”. The same is true for “A - B” and “B - A”.

It’s possible to have a tie. This code:
```
show Spock + Spock
```
should generate this output:
```
Spock tie (winner Spock)
Result = Spock
```

The following unit tests verify the correct behavior of your DSL. Place the test class in the jankenpon_test.rb source file.

# File: jankenpon_test.rb

require 'minitest/autorun'
require 'stringio'
require 'jankenpon'

class JakenponTest < Minitest::Test

  def setup
    @old_stdout = $stdout
    @out = $stdout = StringIO.new
  end

  def teardown
    $stdout = @old_stdout
  end

  def test_simple_cases_plus
    assert_equal Scissors, (Scissors + Paper)
    assert_equal Scissors, (Paper + Scissors)
    assert_equal Paper,    (Paper + Rock)
    assert_equal Paper,    (Rock + Paper)
    assert_equal Rock,     (Rock + Lizard)
    assert_equal Rock,     (Lizard + Rock)
    assert_equal Lizard,   (Lizard + Spock)
    assert_equal Lizard,   (Spock + Lizard)
    assert_equal Spock,    (Spock + Scissors)
    assert_equal Spock,    (Scissors + Spock)
    assert_equal Scissors, (Scissors + Lizard)
    assert_equal Scissors, (Lizard + Scissors)
    assert_equal Lizard,   (Lizard + Paper)
    assert_equal Lizard,   (Paper + Lizard)
    assert_equal Paper,    (Paper + Spock)
    assert_equal Paper,    (Spock + Paper)
    assert_equal Spock,    (Spock + Rock)
    assert_equal Spock,    (Rock + Spock)
    assert_equal Rock,     (Rock + Scissors)
    assert_equal Rock,     (Scissors + Rock)
    assert_equal Scissors, (Scissors + Scissors)
    assert_equal Paper,    (Paper + Paper)
    assert_equal Rock,     (Rock + Rock)
    assert_equal Lizard,   (Lizard + Lizard)
    assert_equal Spock,    (Spock + Spock)
  end

  def test_simple_cases_minus
    assert_equal Paper,    (Scissors - Paper)
    assert_equal Paper,    (Paper - Scissors)
    assert_equal Rock,     (Paper - Rock)
    assert_equal Rock,     (Rock - Paper)
    assert_equal Lizard,   (Rock - Lizard)
    assert_equal Lizard,   (Lizard - Rock)
    assert_equal Spock,    (Lizard - Spock)
    assert_equal Spock,    (Spock - Lizard)
    assert_equal Scissors, (Spock - Scissors)
    assert_equal Scissors, (Scissors - Spock)
    assert_equal Lizard,   (Scissors - Lizard)
    assert_equal Lizard,   (Lizard - Scissors)
    assert_equal Paper,    (Lizard - Paper)
    assert_equal Paper,    (Paper - Lizard)
    assert_equal Spock,    (Paper - Spock)
    assert_equal Spock,    (Spock - Paper)
    assert_equal Rock,     (Spock - Rock)
    assert_equal Rock,     (Rock - Spock)
    assert_equal Scissors, (Rock - Scissors)
    assert_equal Scissors, (Scissors - Rock)
    assert_equal Scissors, (Scissors - Scissors)
    assert_equal Paper,    (Paper - Paper)
    assert_equal Rock,     (Rock - Rock)
    assert_equal Lizard,   (Lizard - Lizard)
    assert_equal Spock,    (Spock - Spock)
  end

  def test_dsl_1
    #---------
    show Spock
    #---------
    assert_equal "Result = Spock\n", @out.string
  end

  def test_dsl_2
    #------------------
    show Spock + Lizard
    #------------------
    assert_equal "Lizard poisons Spock (winner Lizard)\n" \
                 "Result = Lizard\n", \
                 @out.string
  end

  def test_dsl_3
    #------------------
    show Spock - Lizard
    #------------------
    assert_equal "Lizard poisons Spock (loser Spock)\n" \
                 "Result = Spock\n", \
                 @out.string
  end

  def test_dsl_4
    #-------------------------
    show Spock + Lizard + Rock
    #-------------------------
    assert_equal "Lizard poisons Spock (winner Lizard)\n" \
                 "Rock crushes Lizard (winner Rock)\n" \
                 "Result = Rock\n", \
                 @out.string
  end

  def test_dsl_5
    #---------------------------
    show Spock + (Lizard + Rock)
    #---------------------------
    assert_equal "Rock crushes Lizard (winner Rock)\n" \
                 "Spock vaporizes Rock (winner Spock)\n" \
                 "Result = Spock\n", \
                 @out.string
  end

  def test_dsl_6
    #--------------------------------------------
    show Rock + Paper + Scissors + Lizard + Spock
    #--------------------------------------------
    assert_equal "Paper covers Rock (winner Paper)\n" \
                 "Scissors cut Paper (winner Scissors)\n" \
                 "Scissors decapitate Lizard (winner Scissors)\n" \
                 "Spock smashes Scissors (winner Spock)\n" \
                 "Result = Spock\n", \
                 @out.string
  end

  def test_dsl_7
    #--------------------------------------------
    show Rock - Paper - Scissors - Lizard - Spock
    #--------------------------------------------
    assert_equal "Paper covers Rock (loser Rock)\n" \
                 "Rock crushes Scissors (loser Scissors)\n" \
                 "Scissors decapitate Lizard (loser Lizard)\n" \
                 "Lizard poisons Spock (loser Spock)\n" \
                 "Result = Spock\n", \
                 @out.string
  end

  def test_dsl_8
    #-------------------------------------------------
    show((Rock + Paper) - (Scissors + Lizard) + Spock)
    #-------------------------------------------------
    assert_equal "Paper covers Rock (winner Paper)\n" \
                 "Scissors decapitate Lizard (winner Scissors)\n" \
                 "Scissors cut Paper (loser Paper)\n" \
                 "Paper disproves Spock (winner Paper)\n" \
                 "Result = Paper\n", \
                 @out.string
  end

  def test_dsl_9
    #---------------------------------------------
    show Paper + ((Spock + Paper) - Lizard + Rock)
    #---------------------------------------------
    assert_equal "Paper disproves Spock (winner Paper)\n" \
                 "Lizard eats Paper (loser Paper)\n" \
                 "Paper covers Rock (winner Paper)\n" \
                 "Paper tie (winner Paper)\n" \
                 "Result = Paper\n", \
                 @out.string
  end
  
end

Deliverables

Create a compressed tarball file with the full contents of the dsl directory. Call this file dsl.tgz. From a terminal, you can use the following command to create this file (make sure to run it at the same level where the dsl folder resides):

tar czf dsl.tgz dsl

✔ Upload Instructions

To deliver the dsl.tgz file, please provide the following information:

Request PIN

Only one team member needs to upload the file.

Due date is Wednesday, March 30.

S/W Design and Architecture

Domain-Specific Language Pattern

Objectives

Activity Description

Deliverables

✔ Upload Instructions