On 20 April 2015 at 08:44, Jim Mooney <cybervigila...@gmail.com> wrote:
> I can't seem to get my head around this 'simple' book example of
> binary-to-decimal conversion, which goes from left to right:
>
> B = '11011101'
> I = 0
> while B:
> I = I * 2 + int(B[0])
> B = B[1:]
Follow through the loop and see what happens. To begin I is zero and B
is the full string. Consider B_orig to be the original string. After
the first iteration we have that
I = B[0] and B = B_orig[1:]
then
I = 2*B[0] + B[1] and B = B_orig[2:]
then
I = 2*(2*B[0] + B[1]) + B[2] = 4*B[0] + 2*B[1] + B[2]
then
I = 8*B[0] + 4*B[1] + 2*B[2] + B[3]
and eventually
I = 128*B[0] + 64*B[1] + ... + 2*B[6] + B[7]
which is the desired result.
Oscar
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