Is it possible to get a natural log of a big-integ

问题:

I am using big-integer for JavaScript.

var bigInt = require('big-integer')

I have a bigInt instance:

var ratherLargeNumber = bigInt(2).pow(2048)

Can I get a (natural) log of it?

回答1:

Say you have a big integer x = 5384932048329483948394829348923849.

If you convert x to a decimal string and count the digits, you can then represent x by 0.5384932048329483948394829348923849 × 10³⁴.

You want to take the natural logarithm of x. Observe the following.

log_e(x) = 34 log_e(10) + log_e(0.5384932048329483948394829348923849)

You can now use regular Number computations and the regular Math.log to perform the computation.

var bigInt = require('big-integer');
var integer = bigInt('5384932048329483948394829348923849').toString();
var ln_x = Math.log(10 + integer);