rgroshanrg/bigint

bigint is a C++ library which can handle Very very Big Integers. It can calculate factorial of 1000000... it can go any big. It may be useful in Competitive Coding and Scientific Calculations which deals with very very large Integers. It can also be used in Decryption process. It has many inbuilt functions which can be very useful.

bigint's Issues

Ability to print a `bigint`.

Hey there! I would greatly appreciate some sort of ability to print these bigints. I'm not going to suggest how that could be implemented, because I'm not sure, but I figured I'd make an issue to point out that it would be useful 😄

Cannot cast and/or pass bigint type inside [ ]

Using Visual Studio C/C++

Trying to compute large factorials and permutation for n-th lexograohic permutation of arrays/strings.

Code segment:

memmove(buffer, digits, length * sizeof(element_t));

for (i = 0; i < length - 1; i++)
{
    scale /= (permutation_t)(length - i);
    d = index / scale;
    index %= scale;
    z = to_bigint(0);
    if (d > z) 
    {
        bigger_i = to_bigint(i);
        c = buffer[d + bigger_i];
        memmove(buffer + i + 1, buffer + i, smaller_d * sizeof(element_t));
        buffer[i] = c;
    }
}

Fails inside c = buffer[] line of code.

Severity Code Description Project File Line Suppression State
Error C2677 binary '[': no global operator found which takes type 'bigint' (or there is no acceptable conversion)

Top of code (compiles fine)

bigint permutation(element_t* const buffer,
const element_t* const digits,
const element_t length,
bigint index)
{
element_t c;
bigint d, z, scale, bigger_i;
element_t smaller_d, i;

if (!buffer || !digits || length < 1)
    return errno = EINVAL;

...

Please advise.

no operator "+" matches these operands; operand types are: const bigint + const bigint

For the following snippet:

const bigint a("1");
const bigint b("2");
std::cout << a + b << std::endl; // error in this line 

I am getting this error:

no operator "+" matches these operands
operand types are: const bigint + const bigint

Interestingly, removing const from a is resolving this error. I suspect you are internally changing the value of a.

Contribute fixing bugs if any, and decrease time and space Complexity of Algorithms used.

Large division broken

I'm trying to divide 2 large integers, but after a certain point the quotient just becomes 0.

Ex 1:
bigint x("108165236279178312660610114131826512483935470542850824183737259708197206310322");
bigint y("10816523631251238799");
std::cout << "x / y = " << x / y << "\n";
gives 1111110100100100111001001010110100111011000110001110101000

Ex 2:
Adding just one extra integer ends up returning 0
bigint x("108165236279178312660610114131826512483935470542850824183737259708197206310322");
bigint y("108165236312512387996");
std::cout << "x / y = " << x / y << "\n";
gives 0

I've been looking for some kind of bigfloat library that could work, but haven't found any that supports division with such large integers. I'm working on an Elliptic Curve Cryptography implementation and need to divide two large integers (both the same size as x, but y around one digit shorter) for elliptic curve division. If anyone knows any libraries that support the division, I'd appreciate it a lot.

Thanks.

BigInt to String/Int/Long Long Int

I think you should also add methods which could help us to convert BigInt to primitive data types lke integer, string and long long int

we cannot generate big random number ...

We should be able generate a random number from a to b, it would be easier to implement cryptographic algorithms :).

cannot cast bigint to double

tried to cast two bigints to double in order to display their division result accordingly but vs complained no such function available

Had to add this to get it working

I use the single library file and it didn't work if I didn't had inline in front of all internal and public deinifition.
I use C++ 20 with Visual Studio 2022.