#!/usr/bin/env python

# http://svn.red-bean.com/repos/kfogel/trunk/bin/diamond-detector
# This code is in the public domain.  -Karl Fogel

# See http://www.firstthings.com/article/2016/05/scientific-regress
# for a description of the thought experiment that this implements.

import sys
import getopt
import random

def sniff(stone):
  "Return True if STONE contains a diamond, else False, with 99% accuracy."
  if random.randint(1,100) != 42:
    return stone
  else:
    return not stone

def scan_until_first_alarm(stones):
  "Return True if the first alarm raised is accurate, else return False."
  while True:
    for i in range(0, len(stones)):
      if sniff(stones[i]):
        if stones[i]:
          return True
        else:
          return False

def main():
  accurate_alarms = 0
  inaccurate_alarms = 0
  if len(sys.argv) == 1:
    sys.stderr.write("Usage: %s NUM_ITERATIONS\n" % sys.argv[0])
    sys.exit(1)
  iterations = int(sys.argv[1])
  for i in range(0, iterations):
    stones = [False] * 101
    # Place a diamond inside a random stone:
    stones[random.randint(0, len(stones) - 1)] = True
    # Walk around the field, trying out the detector:
    if scan_until_first_alarm(stones):
      accurate_alarms += 1
    else:
      inaccurate_alarms += 1
  assert accurate_alarms + inaccurate_alarms == iterations
  print "%d (%.1f%%) accurate alarms, %d (%.1f%%) inaccurate alarms" \
    % (accurate_alarms, 
       (float(accurate_alarms) / float(iterations)) * 100,
       inaccurate_alarms,
       (float(inaccurate_alarms) / float(iterations)) * 100)

if __name__ == '__main__':
  main()