Calculate b-tree size

calc.coffee

# Take a binary tree of depth D, where the lowest nodes have 1 bit, the second lowest have 2 bits, etc.
# This script finds the number of bits in a tree of depth D.

if process.argv.length isnt 3
  console.log 'Usage: coffee calc.coffee <depth>'
  process.exit()

depth = parseInt process.argv[2]
count = 0
for i in [0...depth]
  count += Math.pow(2, i) * (depth - i)

console.log "there are #{count} bits"

regularNum = (1 << depth) - 1
console.log "this is #{100*count/regularNum}% the b-tree size"