referencing a subhash for generalized ngram counting

[braver]

Here's a working version of the ngram counter with nested dict, wonder
how it can be improved!

lines = ["abra ca dabra",
	"abra ca shvabra",
	"abra movich roman",
	"abra ca dabra",
	"a bra cadadra"]

ngrams = [x.split() for x in lines]

N = 3
N1 = N-1

orig = {}

for ngram in ngrams:
	h = orig
	# iterating over i, not word, to notice the last i
	for i in range(N):
	  word = ngram[i]
	  if word not in h:
	    if i < N1: # (*)
	      h[word] = {}
	    else:
	      h[word] = 0
	  if i < N1:
	  	h = h[word]
	  print i, h

	h[word] += 1

print orig


-- e.g., perhaps we could do short-circuit vivification to the end in
(*)?

Cheers,
Alexy