Java number precision

[HeavenAgain]

for example, how do i get the value of 1234 to the power of 7? it reached the number format limit
there must be a way to show it.... BigInteger or BigDecimal? how does those work, if they are related.... and if they are related, i need the log method, which they dont have...

[Euphoracle]

I just googled it:

http://forum.java.sun.com/thread.jspa?threadID=477276&messageID=2217025

Java:

private static final BigDecimal MAX = new BigDecimal(Double.MAX_VALUE); private static final BigDecimal HALF = new BigDecimal(0.5); public static BigDecimal bigLog(BigDecimal b) {     double s = b.signum();     if (s <= 0.0)         return null; // error     int i = 0;     while (b.compareTo(MAX) > 0) {         b = b.multiply(HALF);         i++;     }     double d = b.doubleValue();     if (i > 0) {         double n = i;         d = Math.pow(d,1.0/n) * 2.0;         d = n * Math.log(d);            } else         d = Math.log(d);     return new BigDecimal(d); }

Also, I do believe that BigDecimal, etc have pow(<num>) as a method.

[HeavenAgain]

ArithmeticException: Non-terminating decimal expansion; no exact representable decimal result.

dont get it :'(

[Euphoracle]

Meaning you have created a non terminating non repeating fraction, which BigDecimal cannot represent becuase it strives for absolute accuracy, and whatnot, perhaps I'm wrong, who knows, etc.

<horrible sentence structure >

[HeavenAgain]

i understand and yet i dont understand
im going to kill myself if i dont get this must, research....!!

edit: im not saying you MUST use BigInteger or BigDecimal, that was just my idea, becuase i dont see how long or double is going to hold a number like 4357186184021382204544 (1234 to the power of 7)

[OneOffDriveByPoster]

HeavenAgain @ Sat Nov 17, 2007 9:42 pm wrote:

i need the log method, which they dont have...

You need log in what base? And are your inputs exact powers of the base? Might be easier if you don't need a general log function.

[HeavenAgain]

input is 2 numbers, n and p
n square root of p, find k (the result)

and if p is 7 and n is 4357186184021382204544, result i should i get is 1234
now n is too big for double or long, thats what im talking about i hope it it helps anyone with helping me

side note, k = 10^((log n)/ p), i think

[Barbarrosa]

I've tried to use BigDecimal to do it, but to no avail. There is no floating point power, nor any root method for BigDecimal.

[HeavenAgain]

Java's BigDecimal have something weird going on inside, so for this problem, im not sure if it will be suitable for it, becuase

code:

BigDecimal num = new BigDecimal(1.1); System.out.println(num); System.out.println(num.pow(2));

as you can see num is not 1.1, its acually some number with some useless trail of floating point

but back to the problem, there was a hint given, and it said, double should be able to handle it

[Barbarrosa]

Well, Eclipse will accept it if you put it in scientific notation. Won't give me 1234 as an answer, though.

[HeavenAgain]

hehe, never mind about this question, i have figured out the way to solve this type of problem
something about high percision algorith, involving array
thanks for all the inputs

[Barbarrosa]

Welcome, I'm also interested in getting the answer. Could you share it?