PositiveDouble prototype: representing a positive and finite numbers

[ILIYANGERMANOV]

Based on #4 I've implemented a simple PositiveDouble prototype.

TL;DR;

• Unsafe creation via PositiveDouble(5.0) or PositiveDouble.unsafe(-2.0) which throws are exception
• Safe creation using PositiveDouble.fromDouble(a) which returns Option
• Overloads for +, -, *, /, %
• PositiveDouble#mapSafe extension for safely transforming the wrapped Double value
• ArrowExactConstraintViolationError with detailed error message for easier debugging or handling programatically

[ILIYANGERMANOV]

Should we make this less verbose? It's a trade-off between information and verboseness.

[ILIYANGERMANOV]

Should we make this less verbose? It's a trade-off between information and verboseness.

[ILIYANGERMANOV]

Tests couldn't execute so I added this. Idk, if this or the invalidate & restart fixed the issues

[pacher]

Are you sure about operators returning Option? How would the usage look like for more complex formulas with more than one operation? (a - b) * c - d / e etc. It is a primitive, so I guess something like this should be easily doable without dozens of bind in between.
I was thinking more about something along the lines of

context(Raise<ArrowExactConstraintViolationError>)
operator fun plus(other: PositiveDouble): PositiveDouble

and dsl like positive { (a - b) * c - d / e } returning Either<ArrowExactConstraintViolationError, PositiveDouble>
Can't we do that?

Yes, I am suggesting to design it with context receivers from the start and keep experimental/ pre-release until context receivers are landed. I just don't see it any other way for primitives.

P.S. I apologize in advance, I could be totally off track here and misunderstand a lot since I did not even use arrow yet, just reading the new web site.

[ILIYANGERMANOV]

Side note: Don't forget to check #4 which our discussion issue:
Arrow Exact discussion

Feel free to share your thoughts, ideas, and opinions - all are more than welcome!

[ILIYANGERMANOV]

Are you sure about operators returning Option? How would the usage look like for more complex formulas with more than one operation? (a - b) * c - d / e etc. It is a primitive, so I guess something like this should be easily doable without dozens of bind in between. I was thinking more about something along the lines of

context(Raise<ArrowExactConstraintViolationError>)
operator fun plus(other: PositiveDouble): PositiveDouble

and dsl like positive { (a - b) * c - d / e } returning Either<ArrowExactConstraintViolationError, PositiveDouble> Can't we do that?

Yes, I am suggesting to design it with context receivers from the start and keep experimental/ pre-release until context receivers are landed. I just don't see it any other way for primitives.

P.S. I apologize in advance, I could be totally off track here and misunderstand a lot since I did not even use arrow yet, just reading the new web site.

Good point @pacher! I like the Raise idea + Either DSL 👍 Let's discuss in #4. I hope that during the week more people will join and we'll get more POVs - which is normal I'm spamming people with code on Sunday (I usually rest on Sundays but got excited about the Arrow Exact library 😄 )

[pacher]

Also, it feels right to do overloading like

operator fun plus(other: PositiveDouble) = if (...) throw ...

context(Raise<ArrowExactConstraintViolationError>)
operator fun plus(other: PositiveDouble) = if (...) raise ...

but it is actively discouraged ... sigh

[pacher]

And the biggest design question is what to do when mixing with regular primitives. What should be the return type of PositiveDouble - Double? Should it be PositiveDouble and fail when the result is negative? Or should it be just Double? Both seem sound with valid use cases.

[ILIYANGERMANOV]

We decided to use a more generalized design in #4 which makes this PR obsolete.