[Tutor] bin to dec conversion puzzlement

[Alan Gauld]

On 20/04/15 08:44, Jim Mooney 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:]
...
> Both methods work but I just can't see how the first one does.

The key is that the result gets multiplied by 2 each time
so for an N bit number the leftmost digit winds up being
effectively 2**N, which is what you want.

-- 
Alan G
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