a *= b not equivalent to a = a*b

[INADA Naoki]

        if FAIL: rs *= (n-(i-1))/i  # these should be the same,

This is equal to rs = rs * ((n-(i-1))/i)

        else: rs = rs * (n-(i-1))/i  #  but apparently are not

This is equal to rs = (rs * (n-(i-1)))/i



On Fri, Aug 26, 2016 at 3:20 PM, mlz <mlzarathustra at gmail.com> wrote:
> I've been playing with the binomial function, and found that in the below code, rs *= x does not behave the same way as rs = rs * x. When I set FAIL to True, I get a different result.  Both results are below.
>
> I had read that the two were equivalent. What am I missing?
>
> thanks,
>   -= miles =-
>
>
> #!/usr/bin/python2
>
> import sys
> FAIL= True if len(sys.argv)>1 else False
>
> def bin(n,k):
>     rs=1
>     k=min(k,n-k)
>
>     for i in range(1,k+1):
>         if FAIL: rs *= (n-(i-1))/i  # these should be the same,
>         else: rs = rs * (n-(i-1))/i  #  but apparently are not
>     return rs
>
>
> for n in range(10):
>     for k in range(n+1):
>         print bin(n,k),
>     print''
>
> ------------------- output -------------------------
>
>
> $ pascal2
> 1
> 1 1
> 1 2 1
> 1 3 3 1
> 1 4 6 4 1
> 1 5 10 10 5 1
> 1 6 15 20 15 6 1
> 1 7 21 35 35 21 7 1
> 1 8 28 56 70 56 28 8 1
> 1 9 36 84 126 126 84 36 9 1
>
> $ pascal2 fail
> 1
> 1 1
> 1 2 1
> 1 3 3 1
> 1 4 4 4 1
> 1 5 10 10 5 1
> 1 6 12 12 12 6 1
> 1 7 21 21 21 21 7 1
> 1 8 24 48 48 48 24 8 1
> 1 9 36 72 72 72 72 36 9 1
>
>
>
>
> --
> https://mail.python.org/mailman/listinfo/python-list



-- 
INADA Naoki  <songofacandy at gmail.com>