Understood. Even if you keep operators they could be mapped to certain built in
interface methods. C++ has operator loading, Java does not (except for
auto-boxing) It seems Go generics are trying to play in the middle and I think
the end result is going to lead to confusing code, but we shall see.
> On Aug 8, 2020, at 11:16 AM, Ian Lance Taylor <i...@golang.org> wrote:
>
> On Fri, Aug 7, 2020 at 6:54 PM Robert Engels <reng...@ix.netcom.com> wrote:
>>
>> I’d really like to see an example of generic code that takes both string and
>> numeric types that uses operators. Sorting/searching is one but as I already
>> said the built in string operators are not sufficient for collation cases.
>>
>> Even generic code that “only works on unsigned types”.
>>
>> More than 90% of all generic code is collections. Operators are not needed
>> for these.
>
> I don't think I have anything useful to add to what I've said already
> on this topic.
>
> I believe that being able to write a Min function in ordinary Go is an
> absolute requirement for generics in Go. Full stop.
>
> It would be great to hear about any fatal problems that type lists
> have. It would be great to hear about alternative approaches that
> support operators. I don't think it's useful to debate whether we
> need to be able to use operators in generic code.
>
> Ian
>
>
>
>>>> On Aug 6, 2020, at 2:45 PM, burak serdar <bser...@computer.org> wrote:
>>>
>>> On Thu, Aug 6, 2020 at 1:17 PM Ian Lance Taylor <i...@golang.org> wrote:
>>>>
>>>>> On Thu, Aug 6, 2020 at 12:10 PM Robert Engels <reng...@ix.netcom.com>
>>>>> wrote:
>>>>>
>>>>> We’ll probably agree to disagree there. Java has a lot of generic code
>>>>> written and it’s never been a problem (using methods). Rarely can you
>>>>> write code that treats + the same no matter if passed a string or numeric.
>>>>>
>>>>> Even operators like < with strings don’t really make a lot of sense
>>>>> because different collations are used.
>>>>>
>>>>> I think having a higher bar for Go generic implementations is fine -
>>>>> writing generic code properly is harder than regular Go - there’s much
>>>>> more to resin about.
>>>>
>>>> I hope that is not the case.
>>>>
>>>> Also, it's important that it be easy to read generic code. We can put
>>>> extra burdens on writers of generic code if necessary, but we must
>>>> make the burden on readers of generic code as small as we possibly
>>>> can.
>>>>
>>>> And again: is the complexity from requiring methods rather than
>>>> operators really less than the complexity of using type lists?
>>>
>>> There are things you can do with type lists that you cannot do with
>>> operators. You can limit a function to run on unsigned numbers, for
>>> instance. I think it also makes it explicit to the reader that
>>> a.Add(b) is possibly more complicated than a+b.
>>>
>>>>
>>>> Ian
>>>>
>>>>
>>>>
>>>>>> On Aug 6, 2020, at 1:53 PM, Ian Lance Taylor <i...@golang.org> wrote:
>>>>>>
>>>>>> On Wed, Aug 5, 2020 at 8:52 PM Robert Engels <reng...@ix.netcom.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> I understand your point, but I think a few minor corrections Make a
>>>>>>> difference - it does not matter that String supports + and not - , a
>>>>>>> string would not be a Number. String concatenation is not addition.
>>>>>>
>>>>>> My point wasn't that a string is a number. My point was that the
>>>>>> current design draft permits writing a function that uses + and works
>>>>>> with both strings and numbers. If we adopt something along the lines
>>>>>> of what you are suggesting, we must either define a name for "types
>>>>>> that support +" or we must say "you can't write a generic function
>>>>>> that uses + and works with both strings and numbers."
>>>>>>
>>>>>>
>>>>>>> There are also several ways to implement “ordering” with complex
>>>>>>> numbers, even between complex and rational - it’s all a matter of
>>>>>>> definition. There is also the possibility to make complex not a
>>>>>>> Comparable (compile time failure).
>>>>>>
>>>>>> In Go, the types complex64 and complex128 do not support the < <= >= >
>>>>>> operators. That is what I mean when I say that the complex types are
>>>>>> not ordered. I'm not sure it matters that it is possible to define
>>>>>> some ordering on complex numbers; the point is that the language
>>>>>> defines no such ordering, so if you need to use ordering operators you
>>>>>> can't use complex types.
>>>>>>
>>>>>>
>>>>>>> You write the generic code using methods not operators in all cases.
>>>>>>
>>>>>> Ah, I didn't understand that. I think that is a non-starter. I think
>>>>>> it is a requirement that people be able to write (and read) Min as
>>>>>>
>>>>>> if a < b {
>>>>>> return a
>>>>>> }
>>>>>> return b
>>>>>>
>>>>>> Saying that you must write this as, e.g.,
>>>>>>
>>>>>> if a.Less(b) {
>>>>>> return a
>>>>>> }
>>>>>> return b
>>>>>>
>>>>>> means that the generic language is not the normal language. That adds
>>>>>> a massive layer of complexity to using generics: you can no longer
>>>>>> write ordinary Go code for generic functions, you have to write in
>>>>>> this alternative language that is harder to write and harder to read.
>>>>>> You also have to remember a bunch of names for the methods that
>>>>>> correspond to the operators. The design draft works very hard to
>>>>>> avoid these issues.
>>>>>>
>>>>>> In particular, I think that making that requirement would be adding
>>>>>> much more complexity to the language than we get by adding type lists.
>>>>>>
>>>>>> Ian
>>>>>
>>>>
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>>
>
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