Semantics of toString

[bearophile]

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.

Bye,
bearophile