Tyler's wiki

This is an old revision of the document!

---

# gives all possible integer vectors between two endpoints, inclusively.  For example:
# IntVectorRange([0,0,2], [1,1,3]) yields:
#   [0, 0, 2]
#   [1, 0, 2]
#   [0, 1, 2]
#   [1, 1, 2]
#   [0, 0, 3]
#   [1, 0, 3]
#   [0, 1, 3]
#   [1, 1, 3]
# if only one argument is given to __init__, then the range goes from [0,0,...,0] to the vector given
class IntVectorRange(object):
	def __init__(self,start,end=None):
		if end is None:
			end=start
			start=[0] * len(end)
 
		self.start=start
		self.end=end
		self.size = len(start)
		self.delta = [end[i]-start[i]+1  for  i in xrange(self.size)]
		self.len = reduce(lambda x,y: x*y, self.delta, 1)
 
	def __getitem__(self,index): 
		if index >= self.len: raise IndexError
		r = [0] * self.size
		for i in xrange(self.size):
			r[i] = index % self.delta[i] + self.start[i]
			index /= self.delta[i]
		return r
 
	def __len__(self): return self.len
 
# provides a list with all possible subsets of the given list
# (based on a binary IntVectorRange object)
#
# Example: AllCombinations(['alpha','beta','gamma']) yields:
#   []
#   ['alpha']
#   ['beta']
#   ['alpha', 'beta']
#   ['gamma']
#   ['alpha', 'gamma']
#   ['beta', 'gamma']
#   ['alpha', 'beta', 'gamma']
class AllCombinations:
	def __init__(self,items):
		self.vector_range = IntVectorRange([1] * len(items))
		self.items = items
 
	def __getitem__(self,index):
		v = self.vector_range[index]
		return [self.items[i] for i in xrange(len(v)) if v[i]]
 
	def __len__(self): return len(self.vector_range)
 
# for academic purposes only, here's the same class based on inheritence instead of composition
class AllCombinations2(IntVectorRange):
	def __init__(self,items):
		super(AllCombinations2,self).__init__([1] * len(items))
		self.items = items
 
	def __getitem__(self,index):
		v = super(AllCombinations2,self).__getitem__(index)
		return [self.items[i] for i in xrange(len(v)) if v[i]]