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.
> 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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