Decimals -> Fraction strings, my solution

[Remco Gerlich]

Scott wrote in comp.lang.python:
> Hi all,
> 
> I've come up with one solution to my problem. Its probably quite
> inefficient, but it does what I need for now.  Feel free to
> tear it apart and/or give any advice on how to better implement it.
> This code will take either a number or a string (ie '0.5') and return
> a string of the fraction (ie '1/2').  Here it is:

I had been playing with it too. Your method for finding the gcd is very slow.
To find the gcd of two numbers a and b, you substract the lower from the
higher one, until they are equal.

My solution is this, but it only works for 0 < x < 1. For negative numbers,
integers, and bigger numbers you have some more string formatting to do.

def makefract(x):
   assert type(x) == type(1.0) and 0.0 < x < 1
   
   # These lines may count as a hack, but it works
   sx = str(x)
   digits = len(sx)-2
   value = long(sx[2:])
   
   # The fractional representation is "value/(10**digits)".
   # A better representation divides both by the gcd.
   a, b = value, 10L**digits
   GCD = gcd(a,b)
   return "%s/%s" % (a/GCD, b/GCD)

def gcd(a,b):
   while a != b:
      if a < b:
         b = b - a
      else:
         a = a - b
   return a


-- 
Remco Gerlich,  scarblac at pino.selwerd.nl
  1:22am  up 71 days, 13:36,  7 users,  load average: 0.04, 0.11, 0.06