tools/base_converter.py

   1 #!env python
   2 # vim: set fileencoding=utf8
   3 # Created: April 29, 2008
   4 # Created by: Antonio Chavez
   5 #
   6 # Base converter
   7
   8 import sys, os
   9 import Trits
  10
  11 MIN_VAL = 10
  12 LOW_BOUND = ord('A') + MIN_VAL
  13
  14 def int_cnvrt(value, base_frm, base_to):
  15     ''' int_cvrt: convert the number to the left of the decimal place
  16         value: string containing value to convert
  17         from: what base to convert from. Can be positive and negative.
  18             Negative numbers will represent balanced base.  Positive
  19             will represent unbalanced base.
  20         to: what base to convert to.
  21
  22         Example: 3 = unbalanced base 3 (0, 1, 2)
  23                 -3 = balanced base 3 (-1, 0, 1)
  24         Balanced bases can only be odd integers, for the obivious reason
  25             that even numbers are not good candidates for balanced numbering
  26             Example: -4 = (-1, 0, 1, 2) or (-2, -1, 0, 1).  Either system is
  27             not balanced.  Bases must also have a magnitude greater than 1.
  28         For balanced bases greater than 3, a negative number is represented
  29             with an 'i' next to it.
  30             Example: 4i21 => 4(-2)1
  31         Currently conversion balanced bases is not supported.  If balanced
  32             base is entered, the result will be returned in base 10.
  33         A negative sign before the number will negate the result.
  34     '''
  35
  36     # check for magnitude greater than 1
  37     if abs(base_frm) < 2 or abs(base_to) < 2:
  38         print "bases must have magnitude greater than 1"
  39         raise SystemExit
  40
  41     # check for a balanced negative base and derive magnitude
  42     if base_frm < 0 and base_frm*-1%2 != 1:
  43         print "base_from is even: negative bases must be odd integers"
  44         raise SystemExit
  45     elif base_frm < 0:
  46         magnitude_f = (base_frm*-1 - 1)/2
  47     else:
  48         magnitude_f = base_frm
  49     #magnitude_f = abs(base_frm)
  50
  51     if base_to < 0 and base_to*-1%2 != 1:
  52         print "base_to is even: negative bases must be odd integers"
  53         raise SystemExit
  54     elif base_to < 0:
  55         magnitude_t = (base_to*-1 - 1)/2
  56     else:
  57         magnitude_t = base_to
  58     #magnitude_t = abs(base_to)
  59
  60     sum   = 0   # base 10 equivalent summation
  61     neg   = 1   # used when 'i' is encountered, it negates the previous digit
  62     sign  = 1   # sign of summation
  63     count = 1   # amount to multiply next digit by
  64     prev  = 1   # the value of the next digit
  65     cur   = 0   # current digit
  66
  67     if magnitude_f >= MIN_VAL:
  68         max_val = magnitude_f - MIN_VAL
  69
  70     for i in range(len(value) - 1, -1, -1):
  71
  72         if base_frm == -3:
  73             # Base 3 conversion
  74             if value[i] in Trits.trit_integer:
  75                 sum = sum + (Trits.trit_integer[value[i]])*count
  76                 count = count*abs(base_frm)
  77             else:
  78                 print "%s invalid input", value[i]
  79                 raise SystemExit
  80
  81         elif value[i].isdigit():
  82             # 0 <-> 9
  83             cur = int(value[i])
  84
  85             if cur > magnitude_f:
  86                 print "%s: invalid input", value[i]
  87                 raise SystemExit
  88             if i != len(value) -1:
  89                 sum = sum + prev*neg*count
  90
  91                 # reset variables to appropiate values
  92                 neg = 1
  93                 count = count*abs(base_frm)
  94
  95             prev = cur
  96
  97         elif value[i] == '-' and i == len(value) - 1:
  98             # negate the whole number
  99             sign = -1
 100         elif value[i] == 'i':
 101             # negate prev number
 102             neg = -1
 103         elif magnitude_f >= MIN_VAL and value[i].isalpha():
 104             # 10 <-> magnitude_f
 105             cur = ord(value[i].upper()) - LOW_BOUND
 106
 107             if cur > magnitude_f:
 108                 print "%s: invalid input", value[i]
 109                 raise SystemExit
 110
 111             if i != len(value) -1:
 112                 sum = sum + prev*neg*count
 113
 114                 # reset variables to appropriate values
 115                 neg = 1
 116                 count = count*abs(base_frm)
 117
 118             prev = cur
 119
 120         else:
 121             print "%s: invalid input", value[i]
 122             raise SystemExit
 123
 124     if base_frm == -3:
 125         return "" + str(sum)
 126
 127     # sum up remaining digit
 128     sum = sum + prev*neg*count
 129     sum = sign*sum
 130
 131     # return base 10 if desired base is balanced
 132     if base_frm < 0:
 133         return "" + str(sum)
 134
 135     # compute unbalanced conversion
 136     result = ""
 137     quotient = sum
 138     remainder = 0
 139
 140     while quotient != 0:
 141         remainder = quotient%magnitude_t
 142         quotient = quotient/magnitude_t
 143         result = str(remainder) + result
 144
 145     return result
 146
 147 ''' NOTES
 148     useful things to know for implementation
 149     char to int: ord('a') = 97 ASCII
 150     int to char: chr(97)  ASCII
 151     char to int: int('4')
 152     a = "hi6"
 153     a[0].isalpha() => true
 154     a[2].isdigit() => true
 155     a[0].upper()   => "H"
 156     a[2].upper()   => "1"
 157
 158     s.split(".")   => returns list of strings broken up by "."
 159     "1010.3930"    => ["1010", "3930"]
 160
 161     s = ".".join(lis_digits) => combine elements in list by "."
 162 '''
 163
 164 if __name__ == "__main__":
 165     print int_cnvrt("8", 10, 2)
 166
 167     while True:
 168         print ">> ",
 169         line = unicode(sys.stdin.readline(), "utf8")
 170         if len(line) == 0:
 171             break
 172         line = line.strip()
 173         print
 174
 175         val, frm, to = line.split(",")
 176         frm = int(frm)
 177         to  = int(to)
 178
 179         try:
 180             print int_cnvrt(val, frm, to)
 181         except:
 182             print "An error occured:"
 183             traceback.print_exc()
 184