on 07.04.2010 at 21:04 Chad Nelson wrote :
by the way you could store the sign in the MSB of the most significant digit
Maybe I'm mistaken, but I thought that's what two's-complement meant. a number is stored in two's complement in the following way: if it is positive -- MSB is 0 an values is encoded straightforwardly if it is negative -- it is encoded as 'radix^digits - value' e.g. for 32 bit binary ints it is '2^32 - value'
or simply put if 'v' is positive or negative number to encode and 'm' is some modulo (such as 2^32) then a number is encoded as (m - v)%m the advantage is that addition and subtraction works straightforward with no special care about the signs of operands e.g. a + b == (m + a + b)%m or a - b == (m + a - b)%m i may misunderstand all this so better see e.g. http://en.wikipedia.org/wiki/Two's_complement
though i didn't dig the implementation and not sure you have a distinct bool for the sign
Yes, I do.
i suggest to pack the sign in the MSB of the most significant digit to get rid of the bool it still would be a sign-magnitude representation so retrievel would be like digits[n_digits - 1]&(1<<15)/*==0*/ but perhaps you would need to set that bit to 0 during some operations which involves some additional overhead -- Pavel P.S. if you notice a grammar mistake or weird phrasing in my message please point it out