On Tue, Nov 10, 2009 at 9:16 AM, bearophile <bearophileh...@lycos.com> wrote: > Bill Baxter: >> Maybe it's just my ignorance of BigNum issues, but those links look to >> me to be about divsion and not generating string representations. Are >> those somehow synonymous in BigInt land? > > Look the numeral() function inside here from those blog posts: > http://www.dd.chalmers.se/~frejohl/code/div.py > > To convert a positive integer to string you have to keep dividing a number by > 10, and accumulate the modulus as the digit, converted to ['0', '9']. When > the number is zero you are done: > > n = 541489 > result = "" > while n: > n, digit = divmod(n, 10) > result = str(digit) + result # don't do this > print repr(result) # prints '541489' > > But all those large divisions are slow if the number is huge. So that div.py > python program shows a faster algorithm that does something smarter, to > decrease the computational complexity of all that.
Well, anyway, slowness of BigInt is not what Don was referring to. He was talking about the general slowness of a toString interface that forces allocating enough memory to hold the entire result, instead of being able to dole out the result piecemeal. --bb
