Research and explain Boolean type

[razcore-rad]

Context

1. Indicate the affected section (i.e. top-level folder)
   I'm not sure where it would go

2. Indicate what kind of issue this is
   Enhancement = a new idea that can be documented/filed

3. If it applies, indicate the file to which you are referring using non-numerical-ordering names

Body

As it stands, purescript has a Boolean type with true & false values. Beginners such as myself, especially ones coming from haskell where there's the data Bool = True | False definition, might wonder where's True & False in purescript. Or why they're not present. I don't know the full history behind it but I assume it has to do with purescript being so tightly linked with javascript. It can definitely be a point of confusion as one would expect all constructors to start with a capital letters and this being such a simple data type one wouldn't expect literal values for it, or at least it's a bit of a discord compared to basic types.

[JordanMartinez]

psc-package is originally phil and others' project

Yeah... that's a good question 😅 Haha!

I'm coming from a Java background and the true/false values are lower-cased. So, this issue could be solved in one of two ways:

• Add a "Differences from Haskell" file
• Explain how the Javascript backend influenced the syntax of the language (Technically, PureScript could compile to C and Swift depending on which backend one uses.)

I think I like the 'Haskell Differences' idea better because it's the only language I know of that uppercases the true/false values.

Thoughts?

[thomashoneyman]

You may simply want to link to this:
https://github.com/purescript/documentation/blob/master/language/Differences-from-Haskell.md

[JordanMartinez]

@thomashoneyman True. I can't recall whether I'd already linked to that specific page or not (I'm guessing not). However, this particular issue can either be solved by updating that repo's page to include that True/False difference or we restate it here. Either way splits the content into two places.

[razcore-rad]

I don't think you linked to the differences, at least I can't remember either. I think we should update that repo's page + offer a short javascript influence explanation in this repo which would talk about why such a simple data type would need literal values instead of the regular constructors.

[JordanMartinez]

Either way, we should link to that page. My question is, where should that link ideally appear? In the Getting Started folder, I presume?

offer a short javascript influence explanation in this repo which would talk about why such a simple data type would need literal values instead of the regular constructors.

Seems like there should be a Backends section/folder, perhaps in the Getting Started folder.

[razcore-rad]

I think the Backends idea is fine, placed in Getting Started. If you think you want to roll your own 2cents about the literal values true/fasle I think those might be better off in Syntax.

[JordanMartinez]

@razcore-art Would you be willing to submit a PR that includes a small snippet for Haskellers in the Syntax part that explains Boolean's quirk? I'll submit a separate PR that includes the link to the Differences from Haskell page, though if you want to include that in a PR, go for it. I was going to put it in its own section in the Getting Started/Other Imporant Info.md.

[razcore-rad]

I can try and see what happens, you know you're giving this task to a total beginner :). I can link with Purescript differences from Haskell as well.

…

On Fri, Nov 16, 2018 at 10:18 PM JordanMartinez ***@***.***> wrote: @razcore-art <https://github.com/razcore-art> Would you be willing to submit a PR that includes a small snippet for Haskellers in the Syntax part that explains Boolean's quirk? I'll submit a separate PR that includes the link to the Differences from Haskell page, though if you want to include that in a PR, go for it. I was going to put it in its own section in the Getting Started/Other Imporant Info.md. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#139 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABH3pLMT5S1TbZW4bCEXv45CdE5HVD-Hks5uvx2ggaJpZM4YiJb-> .

[JordanMartinez]

you know you're giving this task to a total beginner

And...? Haha! This whole repo is my understanding of PureScript, any and all of which could be wrong, haha! If you happen to contribute something that is wrong, you're in good company. We can learn together.

Still, I don't think this particular issue is that difficult. You're basically saying, "In Haskell, you write True and in PureScript, you write true. Why? Because of the influence of Javascript. Why not change it? Because backwards compatibility and ecosystem stability, etc."

I can link with Purescript differences from Haskell as well.

Ok, thanks!

[razcore-rad]

some notes on research:

a bit of confusion, seems like I'm not the only one: purescript/purescript#842, especially this comment purescript/purescript#842 (comment)
in essence: built-in types aren't ADTs and so it follows they don't have constructors in the regular FP style
explanation in purescript by example: https://leanpub.com/purescript/read#leanpub-auto-simple-types
prim module: https://pursuit.purescript.org/builtins/docs/Prim#t:Boolean - not much explanation, just that we use true/false literal values

[JordanMartinez]

some notes on research:

Mm... that makes a lot more sense.

Rather than using Boolean as the example type that help teach type-level programming's syntax, what if we used a type that works just like Boolean but gets around this suprising-capitalization-syntax issue: YesNo?

[razcore-rad]

YesNo is good

[JordanMartinez]

Mind submitting a PR that changes that?

[razcore-rad]

I can take care of that sure.

[JordanMartinez]

@razcore-art Thanks! And just to make sure this gets done instead of turning into
a "yeah I'll submit a PR. *1 year passes w/o a PR*," I'll wait for a week. If it's not done by then, I'll do it.

[razcore-rad]

Yes, that's acceptable :)

[JordanMartinez]

I've linked to the documentation repo and also a PDF that I also found quite helpful and descriptive (see #156). What are the next actions for this issue?

[razcore-rad]

Your low maintenance work on this repo is far more active than I initially thought :). Yes, I just need to explain in writing why purescript Boolean uses literal true/false values rather than True/False constructors and we'll be good to close this issue. I'll get to it today

[JordanMartinez]

Perhaps I should define "low maintenance": if it requires me to do additional work for a new release each time (e.g. something more than submit development PR on latestRelease branch, summarize new changes, define new tag and release on GH), then it's no longer low maintenance.

If it's fixing bugs or adding new content, I just consider that learning.

I'll get to it today

Excellent!

[razcore-rad]

Well I didn't get to it that day :) but I'm getting to it right now

[AntC2]

You may simply want to link to this: https://github.com/purescript/documentation/blob/master/language/Differences-from-Haskell.md

Looks like nobody did mention true/false vs True/False on that page. That would have saved me some consternation, coming from Haskell.

The world doesn't seem to have blown up if I declare

data Bool = False | True
derive instance eqBool :: Eq Bool 
derive instance ordBool :: Ord Bool 

And a Show instance; and some conversion functions.

[JordanMartinez]

Can you open an issue on the documentaiton repo?