bigi

-module(bigi_ffi).

-export([
    from/1,
    to/1,
    zero/0,
    compare/2,
    add/2,
    subtract/2,
    multiply/2,
    divide/2,
    divide_no_zero/2,
    remainder/2,
    remainder_no_zero/2,
    modulo/2,
    modulo_no_zero/2,
    power/2
]).

from(Int) -> Int.

to(BigInt) -> {ok, BigInt}.

zero() -> 0.

compare(A, B) when A < B -> gt;
compare(A, B) when A > B -> lt;
compare(_, _) -> eq.

add(A, B) -> A + B.

subtract(A, B) -> A - B.

multiply(A, B) -> A * B.

divide(_, 0) -> 0;
divide(A, B) -> A div B.

divide_no_zero(_, 0) -> {error, nil};
divide_no_zero(A, B) -> {ok, divide(A, B)}.

remainder(_, 0) -> 0;
remainder(A, B) -> A rem B.

remainder_no_zero(_, 0) -> {error, nil};
remainder_no_zero(A, B) -> {ok, remainder(A, B)}.

modulo(_, 0) -> 0;
modulo(A, B) -> ((A rem B) + B) rem B.

modulo_no_zero(_, 0) -> {error, nil};
modulo_no_zero(A, B) -> {ok, modulo(A, B)}.

power(_, 0) ->
    1;
power(A, 1) ->
    A;
power(A, N) ->
    B = power(A, N div 2),
    B * B *
        (case N rem 2 of
            0 -> 1;
            1 -> A
        end).