Converting u64 to u256 and vice versa

Sway
1

I’m looking to convert u64 to u256 and vice versa for the Fraction library. I’m unable to find the documentation and reverse engineering the core libs isn’t working out. I was wondering if someone could share the steps needed for this conversion. Thanks

2

If 10 is your number for example

10_u64.as_u256()

This pattern should work for all unsigned integers for converting between the current size and a bigger size. Aka u8 → u16 would be

10_u8.as_u16()

You can see the underlying code here

2 Likes
3

Thanks. Now I can convert u64 to u256. But I also need the reverse conversion. I’ve tried

  1. x.try_into().unwrap()
  2. x.as_u64()
  3. x.to_u64()
  4. x.d
  5. let (a, b, c, d) = x

Where x is of the type u256 but nothing worked.

4

As the reverse conversions are lossy, the standard library offers methods that return an option.

u64::try_from(x)

This will return an option, you can match on it or unwrap it.

5

Doesn’t work for me. Maybe I did something wrong. I’m trying:

let np = u64::try_from((an*bn*factor.as_u256())/(ad*bd)).unwrap();

where all the variables used in the middle are of the nature u256. The error message is:
^^^^^^^^ No method named “try_from” found for type “u64”

I haven’t imported u64 at the top of the file after library; because I don’t believe we have to import primitive types. Am I doing something wrong?

6

Here is the concerned erroring line (ignore the other errors, they only appear when this function isn’t commented out).

7

You dont have to import the type but you do have to import the methods, as they are not imported by default.

use std::primitive_conversions::u64::*;

Should work

1 Like
8

After some changes in addition to that, this error went away. Maybe we could somehow add this to the official documentation?

9

Hi there :palm_tree:
I’m adding this documentation request to the backlog
thanks for your report.