Here below a little program in JRuby that implements 2 classes. There is the main class, called Fiborial (Fibo(nnacci)+(Facto)rial) that implements the Fibonacci and the Factorial algorithms in two ways, one Recursive (using recursion) and the other Imperative (using loops and states). The second class is just an instance class that does the same thing, but its there just to show the difference between static and instance classes, and finally a main function called as module level code.
You can also find 3 more little examples at the bottom. One prints out the Factorial's Series and Fibonacci's Series, the second one just shows a class that mixes both: static and instance members, and finally the third one that uses different return types for the Factorial method to compare the timing and result.
As with the previous posts, you can copy and paste the code below in your favorite IDE/Editor and start playing and learning with it. This little "working" program will teach you some more basics of the Programming Language.
There are some "comments" on the code added just to tell you what are or how are some features called. In case you want to review the theory, you can read my previous post, where I give a definition of each of the concepts mentioned on the code. You can find it here: http://carlosqt.blogspot.com/2011/01/new-series-factorial-and-fibonacci.html
WARNING: the code that you will see below is not following ruby guidelines/idiomatic coding, I did it in purpose to compare ruby's syntax and features side by side with other programming languages... For instance, instead of using a ruby bignum I imported and used java.math.BigInteger instead. Other examples, naming convention and so on, so bear with me!
I'm using the same Stopwatch java class that I used in the Java version of this post. I just added the .class into a 'target' folder and added it to the classpath. then I java_imported it. http://carlosqt.blogspot.com/2011/05/stopwatch-class-for-java.html
The Fiborial Program
# Factorial and Fibonacci in JRuby
require "java"
$CLASSPATH << "target"
java_import 'Stopwatch'
import java.lang.System
import java.math.BigInteger
module FiborialRb
# Static Class
# static classes are not supported in Ruby
class StaticFiborial
# Static Field
@@class_name = ""
# no builtin static constructor/initializer support
# you can initialize field at this point and even add extra code
@@class_name = "Static Constructor"
puts @@class_name
# Static Method - Factorial Recursive
def self.factorial_r(n)
if n < 2
BigInteger.new('1')
else
BigInteger.new(n.to_s).multiply(self.factorial_r(n-1))
end
end
# Static Method - Factorial Imperative
def self.factorial_i(n)
res = BigInteger.new('1')
while n > 1
res = BigInteger.new(res.multiply(n).to_s)
n -= 1
end
res
end
# Static Method - Fibonacci Recursive
def self.fibonacci_r(n)
if n < 2
1
else
self.fibonacci_r(n - 1) + self.fibonacci_r(n - 2)
end
end
# Static Method - Fibonacci Imperative
def self.fibonacci_i(n)
pre = 1
cur = 1
tmp = 0
for i in 2..n
tmp = cur + pre
pre = cur
cur = tmp
end
cur
end
# Static Method - Benchmarking Algorithms
def self.benchmark_algorithm(algorithm, values)
timer = Stopwatch.new
i = 0
testValue = 0
facTimeResult = BigInteger::ZERO
fibTimeResult = 0
# "case/switch" Flow Control Statement
case algorithm
when 1
puts "\nFactorial Imperative:"
# "For in range" Loop Statement
for i in 0..values.size - 1 do
testValue = values[i]
# Taking Time
timer.start
facTimeResult = self.factorial_i(testValue)
timer.stop
# Getting Time
puts " (#{testValue}) = #{timer.elapsed}"
end
when 2
puts "\nFactorial Recursive:"
# "While" Loop Statement
while i < values.size do
testValue = values[i]
# Taking Time
timer.start
facTimeResult = self.factorial_r(testValue)
timer.stop
# Getting Time
puts " (#{testValue}) = #{timer.elapsed}"
i += 1
end
when 3
puts "\nFibonacci Imperative:"
# "until" Loop Statement
until i == values.size do
testValue = values[i]
# Taking Time
timer.start
fibTimeResult = self.fibonacci_i(testValue)
timer.stop
# Getting Time
puts " (#{testValue}) = #{timer.elapsed}"
i += 1
end
when 4
puts "\nFibonacci Recursive:"
# "For each?" Statement
values.each do |testValue|
# Taking Time
timer.start
fibTimeResult = self.fibonacci_r(testValue)
timer.stop
# Getting Time
puts " (#{testValue}) = #{timer.elapsed}"
end
else
puts "DONG!"
end
end
end
# Instance Class
class InstanceFiborial
# Instance Field
@class_name = ""
# Instance Constructor/Initializer
def initialize
@class_name = "Instance Constructor"
puts @class_name
end
# Instance Method - Factorial Recursive
def factorial_r(n)
# Calling Static Method
StaticFiborial::factorial_r(n)
end
# Instance Method - Factorial Imperative
def factorial_i(n)
# Calling Static Method
StaticFiborial::factorial_i(n)
end
# Instance Method - Fibonacci Recursive
def fibonacci_r(n)
# Calling Static Method
StaticFiborial::fibonacci_r(n)
end
# Instance Method - Fibonacci Imperative
def fibonacci_i(n)
# Calling Static Method
StaticFiborial::fibonacci_i(n)
end
end
# Console Program
puts "Static Class"
# Calling Static Class and Methods
# No instantiation needed. Calling method directly from the class
puts "FacImp(5) = #{StaticFiborial::factorial_i(5)}"
puts "FacRec(5) = #{StaticFiborial::factorial_r(5)}"
puts "FibImp(11)= #{StaticFiborial::fibonacci_i(11)}"
puts "FibRec(11)= #{StaticFiborial::fibonacci_r(11)}"
puts "\nInstance Class"
# Calling Instance Class and Methods
# Need to instantiate before using. Calling method from instantiated object
ff = InstanceFiborial.new
puts "FacImp(5) = #{ff.factorial_i(5)}"
puts "FacRec(5) = #{ff.factorial_r(5)}"
puts "FibImp(11)= #{ff.fibonacci_i(11)}"
puts "FibRec(11)= #{ff.fibonacci_r(11)}"
# Create a (Ruby) list of values to test
# From 5 to 50 by 5
values = []
for i in (5..50).step(5)
values << i
end
# Benchmarking Fibonacci
# 1 = Factorial Imperative
StaticFiborial::benchmark_algorithm(1,values)
# 2 = Factorial Recursive
StaticFiborial::benchmark_algorithm(2,values)
# Benchmarking Factorial
# 3 = Fibonacci Imperative
StaticFiborial::benchmark_algorithm(3,values)
# 4 = Fibonacci Recursive
StaticFiborial::benchmark_algorithm(4,values)
# Stop and exit
puts "Press any key to exit..."
gets
end
And the Output is:
Printing the Factorial and Fibonacci Series
require 'java'
import java.lang.StringBuffer
import java.math.BigInteger
module FiborialSeriesRb
class Fiborial
# Using a StringBuffer as a list of string elements
def self.get_factorial_series(n)
# Create the String to hold the list
series = StringBuffer.new
# We begin by concatenating the number you want to calculate
# in the following format: "!# ="
series.append("!")
series.append(n)
series.append(" = ")
# We iterate backwards through the elements of the series
i = n
while i >= 1
# and append it to the list
series.append(i)
if i > 1
series.append(" * ")
else
series.append(" = ")
end
i -= 1
end
# Get the result from the Factorial Method
# and append it to the end of the list
series.append(self.factorial(n).to_s)
# return the list as a string
series.to_s
end
# Using a StringBuffer as a list of string elements
def self.get_fibonnaci_series(n)
# Create the String that will hold the list
series = StringBuffer.new
# We begin by concatenating the first 3 values which
# are always constant
series.append("0, 1, 1")
# Then we calculate the Fibonacci of each element
# and add append it to the list
for i in 2..n
if i < n
series.append(", ")
else
series.append(" = ")
end
series.append(self.fibonacci(i))
end
# return the list as a string
series.to_s
end
def self.factorial(n)
if n < 2
BigInteger.new('1')
else
BigInteger.new(n.to_s).multiply(self.factorial(n-1))
end
end
def self.fibonacci(n)
if n < 2
1
else
self.fibonacci(n - 1) + self.fibonacci(n - 2)
end
end
end
# Printing Factorial Series
puts ""
puts Fiborial::get_factorial_series(5)
puts Fiborial::get_factorial_series(7)
puts Fiborial::get_factorial_series(9)
puts Fiborial::get_factorial_series(11)
puts Fiborial::get_factorial_series(40)
# Printing Fibonacci Series
puts ""
puts Fiborial::get_fibonnaci_series(5)
puts Fiborial::get_fibonnaci_series(7)
puts Fiborial::get_fibonnaci_series(9)
puts Fiborial::get_fibonnaci_series(11)
puts Fiborial::get_fibonnaci_series(40)
# Stop and exit
puts "Press any key to exit..."
gets
end
And the Output is:
Mixing Instance and Static Members in the same Class
Instance classes can contain both, instance and static members such as: fields, properties, constructors, methods, etc.
require 'java'
# Instance Class
class Fiborial
# Instance Field
@instance_count = 0
# Static Field
@@static_count = 0
# Instance Read-Only Getter
def get_instance_count()
@instance_count
end
# Static Read-Only Getter
def self.get_static_count()
@@static_count
end
# Instance Constructor/Initializer
def initialize()
@instance_count = 0
puts "\nInstance Constructor #{@instance_count}"
end
# No Static Constructor/Initializer
# You can do a self.initialize() static method, but it will not be called
#def self.initialize()
# @@static_count = 0
# puts "\nStatic Constructor #{@@static_count}"
# Instance Method
def factorial(n)
@instance_count += 1
puts "\nFactorial(#{n.to_s})"
end
# Static Method
def self.fibonacci(n)
@@static_count += 1
puts "\nFibonacci(#{n.to_s})"
end
# Calling Static Constructor and Methods
# No need to instantiate
Fiborial::fibonacci(5)
# Calling Instance Constructor and Methods
# Instance required
fib = Fiborial.new
fib.factorial(5)
Fiborial::fibonacci(15)
fib.factorial(5)
# Calling Instance Constructor and Methods
# for a second object
fib2 = Fiborial.new
fib2.factorial(5)
puts ""
# Calling Static Getter
puts "Static Count = #{Fiborial::get_static_count}"
# Calling Instance Property of object 1 and 2
puts "Instance 1 Count = #{fib.get_instance_count}"
puts "Instance 2 Count = #{fib2.get_instance_count}"
gets
end
And the Output is:
Factorial using int, float, System.Numerics.BigInteger
So, it looks like integers in ruby can hold big integers (they are handled as bignum), so using JRuby int/long or java.math.BigInteger is the same so not much to say here.
require 'java'
$CLASSPATH << "target"
java_import 'Stopwatch'
import java.math.BigInteger
# Int/Long Factorial
def factorial_int(n)
if n == 1
1.to_i
else
(n * factorial_int(n - 1)).to_i
end
end
# double/float Factorial
def factorial_float(n)
if n == 1
1.0
else
(n * factorial_float(n - 1)).to_f
end
end
# BigInteger Factorial
def factorial_bigint(n)
if n == 1
BigInteger.new('1')
else
BigInteger.new(n.to_s).multiply(factorial_bigint(n-1))
end
end
timer = Stopwatch.new
facIntResult = 0
facDblResult = 0.0
facBigResult = BigInteger.new('0')
i = 0
puts "\nFactorial using Int/Long"
# Benchmark Factorial using Int64
for i in (5..50).step(5)
timer.start
facIntResult = factorial_int(i)
timer.stop
puts " (#{i.to_s}) = #{timer.elapsed} : #{facIntResult}"
end
puts "\nFactorial using Float/Double"
# Benchmark Factorial using Double
for i in (5..50).step(5)
timer.start
facDblResult = factorial_float(i)
timer.stop
puts " (#{i.to_s}) = #{timer.elapsed.to_s} : #{facDblResult.to_s}"
end
puts "\nFactorial using BigInteger"
# Benchmark Factorial using BigInteger
for i in (5..50).step(5)
timer.start
facBigResult = factorial_bigint(i)
timer.stop
puts " (#{i.to_s}) = #{timer.elapsed.to_s} : #{facBigResult.to_s}"
end
gets
And the Output is:
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