Poor documentation of List*

[Hendrik Boom]

In the Typed Racket Reference, List* is defined as follows:

(List* t t1 ... s)

is equivalent to (Pairof t (List* t1 ... s)).

Following this definition down, we get

(List* a b c)
-> (Pairof a (List* b c))
-> (Pairof a (Pairof b (List* c)))

But what's (List* c) ?

I see no explanatory examples.

-- hendrik

P.S. I'm also unsure what 'bound' is supposed to do in

(List t ... trest ... bound)

It says "where bound must be an identifier denoting a type variable
bound with ..." but I don't undestand what this is referring to.

There are no examples of this in the document, just as there are no
examples of List*.

-- hendrik

[Stephen De Gabrielle]

Hi Hendrik, 

I can't see the example you mention in 

https://docs.racket-lang.org/ts-reference/type-ref.html#%28form._%28%28lib._typed-racket%2Fbase-env%2Fbase-types-extra..rkt%29._.List%2A%29%29

i'm assuming (List* c) is shorthand for (Pair c null)? I don't know typed racket so I've probably got that terribly wrong. 

So while I can't help you with this - I wanted to encourage you to make a PR to the documentation if you come up with a fix.

It *used* to be hard to find the file that needs the fix, good steps have been made recently to make it easier to identify the documentation source file so it is easier to find and make the corrections or additions.

If you have any trouble let me know and I'll try help - I think I'm getting the hang of it.

Hope you are well

Kind regards

Stephen

ps i use https://blog.racket-lang.org/2017/09/tutorial-contributing-to-racket.html & lots of kind guidance from other racketeers :0

pps: if you make a successful pr you get credit in the frankly wonderful racket news https://racket-news.com/2020/06/racket-news-issue-32.html

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[Hendrik Boom]

On Wed, Jun 03, 2020 at 04:22:41PM +0100, Stephen De Gabrielle wrote:
> Hi Hendrik,
>
> I can't see the example you mention in
> https://docs.racket-lang.org/ts-reference/type-ref.html#%28form._%28%28lib._typed-racket%2Fbase-env%2Fbase-types-extra..rkt%29._.List%2A%29%29
>
> i'm assuming (List* c) is shorthand for (Pair c null)? I don't know typed
> racket so I've probably got that terribly wrong.

It might be. But that's normally said as (List c), not List* c)
With your interpretation, List* qould be equivalent to List.

>
> So while I can't help you with this - I wanted to encourage you to make a
> PR to the documentation if you come up with a fix.

My problem is that I don't know what the documentation is supposed to say.

-- hendrik

> To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CAGHj7-LsML%2BeOnt_BUBWmRM5vU6GtovyaNr-JHOQPzoMCL2NTQ%40mail.gmail.com.

[Sam Tobin-Hochstadt]

`(List* T)` is just `T`. This follows the behavior of the `list*`
function, where `(list* 5)` produces 5.

You can explore this using the `:type` form at the REPL. For example,

```
> (:type (List* String))
String
> (:type (List* String String))
(Pairof String String)
> (:type (List* String (List String)))
(List String String)
```

I've pushed a clarification to the documentation.

> To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/20200603194902.27zjystdhecumoup%40topoi.pooq.com.

[Ryan Culpepper]

`(List* T)` is the same as `T`, just as `(list* x)` is the same as `x` (whether `x` is a list or not).

  > (require typed/racket)

  > (list* 4 5 6)
  - : (List* Positive-Byte Positive-Byte Positive-Byte)

  '(4 5 . 6)

  > (list* 6)
  - : Integer [more precisely: Positive-Byte]
  6

  > (:type (List* String))
  String

Ryan

To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/20200603194902.27zjystdhecumoup%40topoi.pooq.com.