Class: Factorial

Inherits:
Object
  • Object
show all
Defined in:
lib/factorial-cached/Factorial.rb

Constant Summary collapse

@@cache = 
{ 
  0 => 1, 1 => 1, 2 => 2, 3 => 6, 4 => 24, 5 => 120, 6 => 720, 7 => 5040, 8 => 40320, 9 => 362880, 10 => 3628800, 11 => 39916800, 12 => 479001600, # Below 32 bit
  14 => 87178291200, 20 => 2432902008176640000, 30 => 265252859812191058636308480000000, 50 => 30414093201713378043612608166064768844377641568960512000000000000, # Milestones for 1-100!
  70 => 11978571669969891796072783721689098736458938142546425857555362864628009582789845319680000000000000000,
  85 => 281710411438055027694947944226061159480056634330574206405101912752560026159795933451040286452340924018275123200000000000000000000,
  100 => 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000 
}
@@default = 
{ :cache => :cache_one, :algorithm => :recursive, :closest => :factorial }

Class Method Summary collapse

Class Method Details

.closest(number, option = ) ⇒ Object 



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# File 'lib/factorial-cached/Factorial.rb', line 36

def closest(number, option = @@default[:closest])
  close = (@@cache.keys.sort{ |x, y| (x - number).abs <=> (y - number).abs })[0];
  return option == :value  ? @@cache[close] : close;
end

.empty_cache(range = nil) ⇒ Object 



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# File 'lib/factorial-cached/Factorial.rb', line 15

def empty_cache( range = nil )
  if range != nil then
    range.each{ |key| @@cache.delete(key); };
    @@cache[0] = 1;
  else @@cache = {0 => 1};  end
end

.factorial(number, *options) ⇒ Object 



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# File 'lib/factorial-cached/Factorial.rb', line 72

def factorial(number, *options)
    
  return @@cache[number] if @@cache.has_key?(number);
  return 1 if (number = number.to_i) <= 0 || !number.is_a?(Integer);     
    
  factorial = method(options.include?(:iterative) ? :iterative_factorial : 
            options.include?(:recursive) ? :recursive_factorial :
              options.include?(:auto) ? (number > 100000 ? :iterative_factorial : :recursive_factorial) : 
                @@default[:algorithm] == :recursive ? :recursive_factorial : 
                    @@default[:algorithm] == :auto ? (number > 100000 ? :iterative_factorial : recursive_factorial) : :iterative_factorial);
  cache = options.include?(:cache_none) ? :cache_none : options.include?(:cache_all) ? :cache_all : options.include?(:cache_one) ? :cache_one : @@default[:cache]; 
  
  result = factorial.call(number, cache);

  @@cache[number] = result if cache != :cache_none;
  
  return result;

end

.get_cache ⇒ Object 



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# File 'lib/factorial-cached/Factorial.rb', line 22

def get_cache()
  return @@cache;
end

.iterative_factorial(number, cache = ) ⇒ Object 



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# File 'lib/factorial-cached/Factorial.rb', line 56

def iterative_factorial(number, cache = @@default[:cache])

  closest = self.closest(number, :factorial);
  loopThrough = closest < number ? ((closest + 1)..number) : ((number + 1)..closest);
  result = @@cache[closest];     

  for i in loopThrough do
    
    if closest < number then result *= i; else result /= i; end
    @@cache[i] = result if cache == :cache_all;

  end
  
  return result;
end

.recursive_factorial(number, cache = , close = -1)) ⇒ Object 



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# File 'lib/factorial-cached/Factorial.rb', line 41

def recursive_factorial(number, cache = @@default[:cache], close = -1)
  
  return @@cache[number] if close == number;

  if close == -1 then
    close = self.closest(number, :factorial);
  end

  result = close < number ? number * recursive_factorial(number - 1, cache, close) : recursive_factorial(number + 1, cache, close) / (number + 1);
  
  @@cache[number] = result if cache == :cache_all;

  return result;
end

.toggle(setting, default) ⇒ Object 



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# File 'lib/factorial-cached/Factorial.rb', line 26

def toggle(setting, default)
  if setting == :cache then
    @@default[:cache] = default;
  elsif setting == :algorithm then
    @@default[:algorithm] = default;
  elsif setting == :closest then
    @@default[:closest] = default;
  end
end