Natural / Integer syntax suggestion

[sellout]

tl;dr: Change the grammar to move the + sigil to Integers and Doubles, like

Natural <- [0-9]+
Integer <- [+-] [0-9]+
Double <- [+-] [0-9]* '.' [0-9]+

I have a few justifications for this:

• personal: Using Dhall at work, we tend to mostly use Natural, with Integer and Double being extremely rare (I find this true of coding in Haskell, as well – it’s mostly the lack of availability of Naturals that makes it not the case in other languages, IMO, although I know it does also depend on the domains that one works in)
• mnemonics: “signed” vs “unsigned” numbers, also “natural” in the sense of “unadorned”
• syntax: Since Natural is the only numeric type with operations, so +2 + +3 is, to me, much harder to read than 2 + 3
• cardinality(?): I think encouraging smaller types is good practice, and simpler syntax for Naturals than Integers should help with that

I know it’s also a significant breaking change across like every config file ever, so …

[Gabriella439]

Yeah, it's a pretty breaking change, but I still think it's a good idea and I agree with all the points you made. I think it's mainly a matter of giving this issue more visibility so that people can chime in about whether or not they think the disruption is worth the benefit. I'll try to broadcast this more widely.

[joneshf]

I 100% support this!

[KirinDave]

I think the cleanup to arithmetic is worth it.

[vmchale]

@sellout I would note that the cardinality is the same in either case.

[sellout]

@vmchale Yeah, that‘s why I added the “(?)” 😄 I just didn’t have a better term for it.

[Gabriella439]

Also, this would probably also change the behavior of Natural/show and Integer/show, which would be a good thing, since most people want to render Natural numbers directly to unsigned numbers (i.e. just use Natural/show n instead of Integer/show (Natural/toInteger n))

One consequence of this would be that there would be no way to render a positive Integer as an unsigned number, but I think that's an acceptable loss

[evincarofautumn]

Sounds like a good idea. A small conversion utility might be helpful for upgrading. I dunno how many users Dhall has at the moment, but it’s a very new language, and IMO people should expect some breaking changes while the core language is being figured out.

[f-f]

I totally agree with all of this thread 👍

[Gabriella439]

Seems like unanimous agreement to me. If nobody objects by tomorrow then we should proceed with a pull request to change the semantics.

@sellout: Did you want to submit the pull request? If not, I can do so

[Gabriella439]

I put up a pull request with the proposed change to the grammar and semantics in #141