Also, even Decimal.compare/2 choses to support this which comforted me with
this decision:

iex> Decimal.compare(Decimal.new(2), 1.0)
** (ArgumentError) implicit conversion of 1.0 to Decimal is not allowed.
Use Decimal.from_float/1

Le sam. 4 mars 2023 à 18:34, Sabiwara Yukichi <sabiw...@gmail.com> a écrit :

> Thank you José for the feedback!
>
> I considered this point, and although it would be ideal, I decided to
> consider this case an acceptable trade-off not to handle it, because:
> 1. it would make the implementation much more complex as pointed out
> 2. it would remove a lot of potential for optimizations
> 3. it might not be such a common huge case, because programs tend to work
> with a given type, mixing them is not so common
>
> I'm a) guarding against number-decimal comparisons and b) handling
> semantic decimal-decimal comparisons, which should cover the two main
> pitfalls with decimals in my experience:
>
> iex> max(Decimal.new(2), Decimal.from_float(1.0))#Decimal<1.0>
>
> iex> Cmp.max(Decimal.new(2), Decimal.from_float(1.0))#Decimal<2>
>
> iex> Cmp.max(Decimal.new(2), 1.0)
> ** (Cmp.TypeError) Failed to compare incompatible types - left: #Decimal<2>, 
> right: 1.0
>
>
> Le sam. 4 mars 2023 à 17:00, José Valim <jose.va...@dashbit.co> a écrit :
>
>> We had discussions in the past and the issue with a Comparable protocol
>> is that we need multiple dispatch. For example, we should be able to
>> semantically compare "Integer cmp Decimal" and "Decimal cmp Integer" which
>> is a more complex problem as it requires defining a scale to compare all of
>> them. Then you can add a compare numbers functionality that converts them
>> to said scale using a separate protocol. It will still require at least two
>> protocol dispatches.
>>
>> On Sat, Mar 4, 2023 at 7:32 AM Sabiwara Yukichi <sabiw...@gmail.com>
>> wrote:
>>
>>> > It's great that there exists a total order (structural) in
>>> Elixir/Erlang, I just wish it wasn't accessible with `<`, `>`, as it is too
>>> error prone and is simply never what one wants to do (at least in our app).
>>> Elixir 2.0? 😆
>>>
>>> (another shameless plug) Your comment motivated me to release this
>>> project I was working on: https://github.com/sabiwara/cmp.
>>> Feedback welcome :)
>>>
>>> Le sam. 4 mars 2023 à 01:26, Marc-André Lafortune <
>>> marc-an...@marc-andre.ca> a écrit :
>>>
>>>> It's great that there exists a total order (structural) in
>>>> Elixir/Erlang, I just wish it wasn't accessible with `<`, `>`, as it is too
>>>> error prone and is simply never what one wants to do (at least in our app).
>>>> Elixir 2.0? 😆
>>>>
>>>> At work I just recently overloaded them to raise unless both arguments
>>>> are `is_number`, and we found bugs where we were comparing Decimals, and
>>>> other bugs where we were comparing with `nil`. They are no longer allowed
>>>> in guards too.
>>>>
>>>> On Friday, 3 March 2023 at 09:31:28 UTC-5 william.l...@cargosense.com
>>>> wrote:
>>>>
>>>>> > if I’m remembering `DateTime.compare/2` correctly
>>>>>
>>>>> Close! The `Module.compare/2` functions return one of `:lt`, `:eq`, or
>>>>> `:gt` ("less than", "equal to", "greater than"), similar to what Haskell
>>>>> does. You may have been thinking of something like OCaml where `compare`
>>>>> returns `-1`, `0`, or `1` resp.
>>>>>
>>>>> > So Why don't we implicitly sort it so that it can be compared by
>>>>> inequality sign(> or <)?
>>>>>
>>>>> To clarify, functions like `<` *define* the sort order.
>>>>>
>>>>> Any time you sort a list, you're using a function that compares two
>>>>> elements. Even if you call `Enum.sort/1`, you're implicitly using `<=/2` 
>>>>> as
>>>>> the comparison function. If you want some other sort order, e.g. for
>>>>> semantic ordering of `DateTime`s, then you must supply your own comparison
>>>>> function.
>>>>>
>>>>> The reason that you can use `<` on structs with `CompareChain` is that
>>>>> it uses macros to re-write an expression like
>>>>>
>>>>> `~D[2023-03-03] < ~D[2023-03-04]`
>>>>>
>>>>> as
>>>>>
>>>>> `Date.compare(~D[2023-03-03], ~D[2023-03-04]) == :lt`.
>>>>>
>>>>> But that doesn't change the behavior of `<` itself. We're basically
>>>>> stuck with what `<` and the like do. Though as José points out, that's
>>>>> actually a good thing.
>>>>>
>>>>> (Side note, you actually have to call `compare?(~D[2023-03-03] <
>>>>> ~D[2023-03-04], Date)` with `CompareChain` to invoke the re-write. I just
>>>>> wanted the example to be more readable.)
>>>>> On Friday, March 3, 2023 at 3:27:00 AM UTC-5 José Valim wrote:
>>>>>
>>>>>> It is also important to note that both kinds of comparisons are
>>>>>> important to have in a language. The docs for main discuss this:
>>>>>> https://hexdocs.pm/elixir/main/Kernel.html#module-structural-comparison
>>>>>>
>>>>>> On Fri, Mar 3, 2023 at 7:47 AM Austin Ziegler <halos...@gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> In this case, because Elixir is passing the `<` and `>` comparisons
>>>>>>> to the underlying BEAM operations and there’s no overloading to say that
>>>>>>> `left < right` should mean `DateTime.compare(left, right) < 0` and 
>>>>>>> `left >
>>>>>>> right` should mean `DateTime.compare(left, right) > 0` (if I’m 
>>>>>>> remembering
>>>>>>> `DateTime.compare/2` correctly).
>>>>>>>
>>>>>>> `CompareChain` does that, but it’s something that gets opted into.
>>>>>>>
>>>>>>> -a
>>>>>>>
>>>>>>> On Thu, Mar 2, 2023 at 10:42 PM 최병욱 <cbw...@gmail.com> wrote:
>>>>>>>
>>>>>>>> So Why don't we implicitly sort it so that it can be compared by
>>>>>>>> inequality sign(> or <)?
>>>>>>>>
>>>>>>>> 2023년 3월 3일 금요일 오전 10시 3분 25초 UTC+9에 william.l...@cargosense.com님이
>>>>>>>> 작성:
>>>>>>>>
>>>>>>>>> Shameless plug: I wrote a library called `CompareChain` that
>>>>>>>>> allows you to use operators like `<` and `>` on structs like 
>>>>>>>>> `DateTime`.
>>>>>>>>>
>>>>>>>>> Hexdocs: https://hexdocs.pm/compare_chain/readme.html
>>>>>>>>>
>>>>>>>>> On Thursday, March 2, 2023 at 10:54:08 AM UTC-5 Jay Rogov wrote:
>>>>>>>>>
>>>>>>>>>> Because the underlying structure used to represent DateTime is a
>>>>>>>>>> struct, which is simply a map under the hood.
>>>>>>>>>> Erlang/Elixir uses a rather arbitrary order of keys (e.g. hour ->
>>>>>>>>>> year -> day -> minute) when comparing 2 maps which you can't control.
>>>>>>>>>>
>>>>>>>>>> Thus, you need to have a specific function that would compare
>>>>>>>>>> these structs according to implied field order (year -> month -> day 
>>>>>>>>>> ->
>>>>>>>>>> hour -> etc.)
>>>>>>>>>>
>>>>>>>>>> More:
>>>>>>>>>> https://hexdocs.pm/elixir/main/NaiveDateTime.html#module-comparing-naive-date-times
>>>>>>>>>>
>>>>>>>>>> On Thursday, 2 March 2023 at 4:38:00 pm UTC+1 cbw...@gmail.com
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> Can't you compare DateTime with '>' or '<' instead of
>>>>>>>>>>> DateTime.compare?
>>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>> You received this message because you are subscribed to the Google
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>>>>>>>> To view this discussion on the web visit
>>>>>>>> https://groups.google.com/d/msgid/elixir-lang-core/afa3830a-8944-4e12-84cc-d8e28d9fceb0n%40googlegroups.com
>>>>>>>> <https://groups.google.com/d/msgid/elixir-lang-core/afa3830a-8944-4e12-84cc-d8e28d9fceb0n%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>>>>>> .
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Austin Ziegler • halos...@gmail.com • aus...@halostatue.ca
>>>>>>> http://www.halostatue.ca/http://twitter.com/halostatue
>>>>>>>
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>>>>>>> .
>>>>>>>
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