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@tomtung
Created March 4, 2012 15:30
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SaaS Class Homework: Ruby Basics
# Homework 1 - Part 1
def palindrome?(string)
string = string.downcase.gsub(/\W/, '')
string == string.reverse
end
def count_words(string)
Hash[
string.downcase.scan(/\w+/).
group_by{|s| s}.
map{|kv| [kv[0], kv[1].size]}]
end
# Homework 1 - Part 2
class WrongNumberOfPlayersError < StandardError ; end
class NoSuchStrategyError < StandardError ; end
def lose?(mine, his)
mine.upcase!; his.upcase!
strategies = ['R', 'P', 'S']
if(!strategies.include?(mine) or !strategies.include?(his))
raise NoSuchStrategyError
end
["RP", "PS", "SR"].include?(mine + his)
end
def rps_game_winner(game)
raise WrongNumberOfPlayersError unless game.length == 2
if(lose?(game[0][1], game[1][1]))
game[1]
else
game[0]
end
end
def rps_tournament_winner(game)
if(game[0][0].kind_of?(String))
rps_game_winner(game)
else
rps_game_winner [rps_tournament_winner(game[0]), rps_tournament_winner(game[1])]
end
end
# Homework 1 - Part 3
def combine_anagrams(words)
words.group_by{|w| w.downcase.chars.sort.to_s}.values
end
# Homework 1 - Part 4
class Dessert
def initialize(name, calories)
@name = name
@calories = calories
end
attr_accessor :name
attr_accessor :calories
def healthy?
@calories < 200
end
def delicious?
true
end
end
class JellyBean < Dessert
attr_accessor :flavor
def initialize(name, calories, flavor)
super(name, calories)
@flavor = flavor
end
def delicious?
@flavor != "black licorice"
end
end
# Homework 1 - Part 5
class Class
def attr_accessor_with_history(attr_name)
attr_name = attr_name.to_s
attr_reader attr_name
attr_reader attr_name+"_history"
class_eval %Q{
def #{attr_name}=(value)
if(!defined?(@#{attr_name}_history))
@#{attr_name}_history = [@#{attr_name}]
end
@#{attr_name} = value
@#{attr_name}_history << value
end
}
end
end
# Homework 2 - 1 - a
class Numeric
@@currencies = {'dollar' => 1.0, 'yen' => 0.013, 'euro' => 1.292, 'rupee' => 0.019}
def method_missing(method_id)
singular_currency = to_singular(method_id)
if @@currencies.has_key?(singular_currency)
self * @@currencies[singular_currency]
else
super
end
end
def in(currency)
singular_currency = to_singular(currency)
if @@currencies.has_key?(singular_currency)
self / @@currencies[singular_currency]
else
super
end
end
private
def to_singular(word)
word.to_s.gsub( /s$/, '')
end
end
# Homework 2 - 1 - b
class String
def palindrome?
# Calls palindrome?(s) defined in Homework 1
Object.send(:palindrome?, self)
end
end
# Homework 2 - 1 - c
module Enumerable
def palindrome?
self.collect{|x| x} == self.collect{|x| x}.reverse
end
end
# Homework 2 - 2
class CartesianProduct
include Enumerable
attr_reader :l_enum, :r_enum
def initialize(l_enum, r_enum)
@l_enum = l_enum
@r_enum = r_enum
end
def each
self.l_enum.each {
|l| self.r_enum.each {
|r| yield [l, r]
}
}
end
end
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