thanks a lot, in my understand, the function under a function can use its
father's type and without convert to templates, and can you explain more
about why there is a make sort stable commet at the second picture which is
the code in the book i download from ats lang web
在2025年6月4日星期三 UTC+8 06:53:07<gmhwxi> 写道：
> For instance, I see the following kind of recursive templates very often:
>
> fun{a:t@ype}
> list0_length(xs: list0(a)): int =
> case+ xs of
> | list0_nil() => 0
> | list0_cons(x1, xs) => 1 + list0_length<a>(xs)
>
> This kind of code may be working, but should be avoided. Instead,
> one can replace it with the following code:
>
> fun{a:t@ype}
> list0_length(xs: list0(a)): int =
> length(xs) where
> {
> fun length(xs: list0(a)): int =
> case+ xs of
> | list0_nil() => 0
> | list0_cons(_, xs) => 1 + length(xs)
> }
>
> BTW, recursive templates, by default, are not supported in ATS3.
>
> On Tuesday, June 3, 2025 at 6:45:35 PM UTC-4 gmhwxi wrote:
>
>>
>> I see that you wrote some ATS2 code.
>>
>> Unfortunately, there is not much written documentation on ATS2 (or ATS in
>> general).
>> It is often difficult for one to immediately figure out how various
>> features in ATS2 should
>> be used.
>>
>> In your code, you have some recursive templates (e.g., your template
>> list0RevHelper is
>> recursive).
>>
>> In general, templates should *not* be recursive. In this case,
>> list0RevHelper does not need
>> to be a template in the first place. Just turn it into an ordinary
>> (recursive) function. Then I believe
>> your problem will go away.
>>
>> --Hongwei
>>
>>
>>
>> On Monday, June 2, 2025 at 8:23:32 PM UTC-4 jin wrote:
>>
>>> when i t[image: 2025-06-03 07.57.11.png]ry to use list0_rev (list0_tail
>>> (listo_rev lista)) as initlist function, there notice segment default at
>>> runtime, so i change function to the picture below, error disappear, i want
>>> to know what cause the error, is there any relation between the error and
>>> the "make stable" of the second picture, which seems like not nessesary,
>>> that's really confuse[image: 2025-06-03 07.57.11.png]
>>> [image: 2025-06-03 08.02.32.png][image: 2025-06-03 07.57.11.png]
>>
>>
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