Is it ok to use your custom interger standard in production?

fuel · November 1, 2023, 3:39pm

Hi guys, during the development of Swaylend I developed my custom I64 number standard because at that time I had problems with this standard from sway libs

It works like this: we have a struct I64 with value that represents absolute value and negative that represents a sign and batch of functions and operators

github.com

compolabs/sway-lend/blob/beta-4/contracts/market/src/i64.sw#L3


      
          library;
          
          pub struct I64 {
              value: u64,
              negative: bool,
          }
          
          impl From<u64> for I64 {
              fn from(value: u64) -> Self {
                  Self {value, negative: false}
              }
          
              fn into(self) -> u64 {

I studied how I64 works from sway libs, it takes the number 922333372036854775808u64 which is 2^64 / 2 for zero, and turns out and what is less than it is the negative part of it

github.com

FuelLabs/sway-libs/blob/master/libs/signed_integers/src/i64.sw

library;

use ::common::TwosComplement;
use ::errors::Error;

/// The 64-bit signed integer type.
///
/// # Additional Information
///
/// Represented as an underlying u64 value.
/// Actual value is underlying value minus 2 ^ 63
/// Max value is 2 ^ 63 - 1, min value is - 2 ^ 63
pub struct I64 {
    /// The underlying unsigned number representing the `I64` type.
    underlying: u64,
}

impl I64 {
    /// The underlying value that corresponds to zero value.
    ///

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I think in terms of implementation this approach is more correct, but it imposes a limitation:
we have a positive part of the I64 number commensurate with the u32 dimension and in some places I am stuck with arithmetic overflow, To avoid this I will have to use the I128 standard, which is created from u128, which is created from 2x u64 and I get my code clogged with a bunch of numeric transformations, which significantly increases code complexity

Can you please tell me what the right thing to do is?
I also found this library in swaylibs.

github.com

FuelLabs/sway-libs/blob/master/libs/fixed_point/src/ufp64.sw

library;
// A wrapper library around the u64 type for mathematical functions operating with unsigned 64-bit fixed point numbers.
use std::{math::{Exponent, Power, Root}, u128::U128};

/// The 64-bit unsigned fixed point number type.
///
/// # Additional Information
///
/// Represented by an underlying `u64` number.
pub struct UFP64 {
    /// The underlying value representing the `UFP64` type.
    value: u64,
}

impl From<u64> for UFP64 {
    /// Creates UFP64 from u64. Note that UFP64::from(1) is 1 / 2^32 and not 1.
    fn from(value: u64) -> Self {
        Self { value }
    }

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It looks like it might help me somehow, but I don’t understand how to work with it yet? Is this an implementation of what I was trying to visualize and can I replace my I64 with IFP64?

sandusky · November 6, 2023, 5:42pm

Hi there!
Tough question here.

Not sure if I can provide a specific-compiler optimized answer.

I’ll escalate this.
Thanks for sharing.

fuel · November 26, 2023, 1:49pm

hi, is there any updates?

sandusky · November 26, 2023, 9:47pm

Hi there!

Please consider that our library have not been audited, only tested for us.
It is up to you to use your own implementation.
Not sure if ufp64.sw is the right choice, since it seems that you are trying to work with integers.
If you want to use FuelLab’s library, you should scale up to 128 to avoid potential overflow.

Also, we might check internally if splitting the range into two is the canonical implementation, otherwise it would require some refactor on our side.

Let me know if this works for you

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Is it ok to use your custom interger standard in production?

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