#!/usr/bin/python 
## the shebang above works for Linux...
## ...in FreeBSD use: 
##!/usr/local/bin/python 
# -*- coding: cp1252 -*-
""" Calculates the transition times for the XOR with two delays with arbitrary precision """

#imports
from decimal import *
import os

#constants
Prec = 12           # number of decimal places
getcontext().prec=Prec
iterations = 1000   # counts the number of transitions
Verbose_level = 1   # 1 = normal messages, 2 = debug mode, 0 = silent mode
# tau1 = 1
tau1 = Decimal(1)
# tau2 = 1/phi , the golden ratio
tau2 = Decimal(2)/(Decimal(1)+Decimal(5).sqrt())
# Minimum allowed pulse width
w_min = Decimal("0.000")
# choices of initial conditions:
#ic = Decimal(0)
ic = -tau2
#tn = [ic-max(tau1,tau2),ic-min(tau1,tau2),ic]
tn = [ic]           # list of transitions


# The programs starts here:
# open outputfile
f = open("xor_2delays_"+str(Prec)+"digits.dat",'wt')
if Verbose_level>0: print "output file: ", "xor_2delays_"+str(Prec)+"digits.dat"
f.write("#tau1 = %s, tau2 = %s\n" % (str(float(tau1)), str(float(tau2))) )
f.write("#Prec = %d, iterations = %d\n" % (Prec, iterations) ) 


# main loop:
for i in range(iterations):
    collided1 = False
    collided2 = False
    # calculates the two candidates of future transitions from the first tn 
    # using tn[0], instead of min(tn), could be faster 
    next_t_candidate_1 = min(tn)+min(tau1,tau2)
    next_t_candidate_2 = min(tn)+max(tau1,tau2)
    if Verbose_level>1:            # optionally prints debug information     #
      print "Processing ", min(tn)                                           #
      print "list = %f " % tn[0],                                            #
      for t in tn[1:]:                                                       #
        print ", %f" % float(t),                                             #
      print "\nt1 = %f, t2 = %f" % (next_t_candidate_1, next_t_candidate_2)  #
    if len(tn)>0:        # if we have transitions in the list ...
        for t in tn:     # ... checks, for all of them, if they collide ...
          if (abs(next_t_candidate_1-t) <= w_min):   # ... with candidate 1 ...
            collided1 = True                         # remembers a collision occurred
            if Verbose_level>1: print "removing ", float(t)
            tn.remove(t)                             # removes colliding transition            
    else:
        if Verbose_level>0: print "empty list, stopping now"
        f.close()
        exit()
    if len(tn)>0:
        for t in tn:
          if (abs(next_t_candidate_2-t) <= w_min):   # ... and/or candidate 2
            collided2 = True                         # remembers a collision occurred
            if Verbose_level>1: print "removing ", float(t)
            tn.remove(t)                             # removes colliding transition 
    else:
        if Verbose_level>0: print "empty list, stopping now"
        f.close()
        exit()
    if not(collided1):                              # if the first candidate did not collide
        if Verbose_level>1: print "saving transition at", float(tn[0])
        #f.write("%s\n" % str(float(tn[0])))
        f.write("%s\n" % str(tn[0]))                # saves generating transition as good one 
        tn.append(next_t_candidate_1)               # appends the good candidate do the list
    if not(collided2):                              # if candidate 2 did not collide
        tn.append(next_t_candidate_2)               # appends the good candidate do the list
        if collided1:      # if candidate 1 collided, we haven't saved the good transition yet
          if Verbose_level>1: print "saving transition at", float(tn[0])
          #f.write("%s\n" % str(float(tn[0])))
          f.write("%s\n" % str(tn[0]))              # saves the transition now

    tn = tn[1:]                                     # removes the processed transition
    tn.sort()                                 # sorts the list, to make sure of the right ordering    


# we have almost finished after the main loop
f.close()
if Verbose_level>0: print "finished!"
# pauses on Windows, to give the user a chance of looking at the error messages, just in case
# we can pause (or wait a few seconds) on posix (Linux), too
if os.name=="posix":
  os.system("sleep 1")
else:
  os.system("pause")