ADD: Eq, Ord, and Show instances for JSDate

[eric-corumdigital]

No description provided.

[eric-corumdigital]

Resolves #14

[LiamGoodacre]

fromTime isn't exported or used?

[garyb]

It already exists as fromInstant too, I'd prefer we use that instead.

[eric-corumdigital]

fromTime copes with NaN and out of bound Numbers in the native way, which is not something that makes much sense with Instant.

[garyb]

Can you add the fromTime export? Then I'll finally get this merged in and released.

[garyb]

I guess it disappeared again in the convoluted reversion process 😉

[eric-corumdigital]

@LiamGoodacre I have not the slightest idea of what you are talking about.

[garyb]

Generic instances aren't suitable for JSDate - Generic can only accurately represent values that are PS sum or product types.

[eric-corumdigital]

I agree that this is not an obvious use of Generic but I do not know what the problem is. My understanding of Generic is that it supports encoding and decoding from types constructed from select constructors such as Sum, Argument, and so forth. The choice of these type constructors is clearly to mimic the grammar of ADT definitions so use in that case becomes obvious.

The ADT JSDate is analogous to is:

newtype JSDate = JSDate Number

Hence my choice for the Generic representation. Number is an accurate representaton of JSDate because fromTime <<< getTime = id.

[garyb]

Well, as an example, genericShow is incorrect with this instance. Generic is not meant to be used for foreign types.

[eric-corumdigital]

I am not invested in the intentions of Generic. I am just looking at what Generic actually is.

There is no reason to expect show = genericShow but lets say it is expected that, like show, genericShow should be valid PureScript code to reconstruct the value. In this case the answer is simply to change the constructor name from "JSDate" to "fromTime".

> genericShow (fromTime 0.0)
"(fromTime 0.0)"

I will submit that revision.

[garyb]

To be completely upfront (and well, a more than a little stubborn) I'm probably not going to merge this as long as there's a Generic instance.

Can I ask why the instance is even useful for this type, since you've implemented the other instances that are usually generic derived anyway?

[eric-corumdigital]

No I am glad you are making the discussion straight-forward! Okay, I have reverted the addition of Generics.