app.pony

use "files"
use "collections"

actor Main
  new create(env: Env) =>
		let collector = Collector(env)
		let parser = Parser(collector)
		let caps = recover val FileCaps.set(FileRead).set(FileStat) end
		try
			let path = FilePath(env.root as AmbientAuth, env.args(1), caps)
			with file = File.open(path) do
				for line in file.lines() do
					parser.parse(line)
				end
			end
			parser.done()
		end

actor Parser
	let _collector: Collector

	new create(collector: Collector) =>
		_collector = collector

	be parse(line: String) =>
		try
			let snum = line.substring(0, line.find("\t") - 1)
			let value = snum.u64()
			_collector.collect(value)
		end

	be done() => _collector.done()

actor Collector
	let _env: Env
	var _prev: U64
	var _count: U32
	let _histo: Map[U32,U32]

	new create(env: Env) =>
		_env = env
		_prev = -1
		_count = 0
		_histo = Map[U32,U32](1000)

	be collect(value: U64) => _collect(value)

	fun ref _collect(value: U64) =>
		if value != _prev then
			let c = 1 + try _histo(_count) else 0 end
			_histo.update(_count, c)
			_count = 0
			_prev = value
		else
			_count = _count + 1
		end

	be done() =>
		_collect(-1)
		try _histo.remove(-1) end
		for (k,v) in _histo.pairs() do
			_env.out.print(k.string() + " => " + v.string())
		end

data.txt

12	13
12	14
12	15
12	16
12	17
12	18
12	20
12	21
12	22
12	23

gistfile1.txt

Real dataset:
The `twitter_rv.tar.gz` social graph from http://an.kaist.ac.kr/traces/WWW2010.html