Change to precedence of unary percentage operator in v14 is confusing

[kiprobinsonknack]

In v14, the precedence or the % or mod operator was changed to be equal to multiplication and division. (see: #3303, #3301, #3311)

However, this also affects the unary percentage operator which I think many users will find confusing.

• v13: 100 / 50% = 100 / (50%) = 100 / 0.5 = 200
• v14: 100 / 50% = (100 / 50)% = 2% = 0.02

The unary % operator should have higher precedence than the binary % modulo operator. There are other cases of unary operators having higher precedence than the same symbol used as a binary operator (+ and - work this way).

I believe this would necessitate a major version change (e.g. v15), as this would be a breaking change.

Here is another example that combines the unary and binary percentage operators for evaluating 10 / 200 % % 3:

• MathJS v13: 10 / 200 % % 3 = 10 / ((200%) % 3) = 10 / (2 % 3) = 10 / 2 = 5
• MathJS v14: 10 / 200 % % 3 = ((10 / 200)%) % 3 = ((0.05)%) % 3 = 0.0005 % 3 = 0.0005
• Desired behavior: 10 / 200 % % 3 = (10 / (200%)) % 3 = (10 / 2) % 3 = 5 % 3 = 2

[kiprobinsonknack]

A little more example of how other platforms handle the unary percent operator:

Wolfram alpha is interesting because it initially assumes % is a unit and behaves like mathjs 14:

But if you convert to a percentage calculation it behavse like mathjs v13:

[josdejong]

Thanks for your input @kiprobinsonknack. It would be neat to improve the behavior of the percentage operator if possible to align with the common expectations. Help would be very welcome.

[kiprobinsonknack]

@josdejong I have a fix ready. How do I contribute to your repository? I cloned it and created a branch, committed my changes to it, but upon git push I get:

ERROR: Permission to josdejong/mathjs.git denied to kiprobinsonknack.

[dvd101x]

Hi, just a quick suggestion.

I think it's more typical to make your own fork of mathjs and then from that fork make a pull request. As a reference #3427

For more in detail explanation you could check
https://docs.github.com/en/get-started/exploring-projects-on-github/contributing-to-a-project

If you have various fixes you could use various branches of your own fork and then make pull requests on those.

[kiprobinsonknack]

PR created: #3432

[josdejong]

We've just released v15.0.0 with the improved behavior of the percentage operator