Large u256 literals

FossilFrank · November 19, 2023, 8:08pm

I’m trying to define a large number in a Sway unit test, but getting the following issue:

280 |   let expected: u256 = 160149899619106589403934712464197979;
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ int literal out of range

How can I define large integers?

diyahir · November 20, 2023, 9:31am

github.com

FuelLabs/sway/blob/master/sway-lib-std/src/u256.sw

//! A 256-bit unsigned integer type.
library;

use ::assert::*;
use ::convert::From;
use ::result::Result::{self, *};
use ::u128::U128;
use ::math::Power;

/// Left shift a `u64` and preserve the overflow amount if any.
fn lsh_with_carry(word: u64, shift_amount: u64) -> (u64, u64) {
    let right_shift_amount = 64 - shift_amount;
    let carry = word >> right_shift_amount;
    let shifted = word << shift_amount;
    (shifted, carry)
}

/// Right shift a `u64` and preserve the overflow amount if any.
fn rsh_with_carry(word: u64, shift_amount: u64) -> (u64, u64) {
    let left_shift_amount = 64 - shift_amount;

This file has been truncated. show original

pub struct U256 {
    /// The most significant 64 bits of the `U256`.
    a: u64,
    /// The 65-128th most significant bits of the `U256`.
    b: u64,
    /// The 129-192nd most significant bits of the `U256`.
    c: u64,
    /// The 193-256th most significant bits of the `U256`.
    d: u64,
}

I don’t think it can just take the raw number, I believe you need to decompose your number into 4 64 bit pieces and then reconstruct it

FossilFrank · November 20, 2023, 8:06pm

I’m trying to use the native u256, not the U256 library.

I worded around it by converting to hex and using the 0x1234u256 notation. But would still be nice to have decimal literals as well.

calldelegation · November 20, 2023, 10:46pm

Yes, @FossilFrank, that is the correct way to do it. I will bring this up with the team to discuss implementing decimal literals.