• Andrei Alexandrescu (11/11) Oct 17 2021 According to https://github.com/dlang/phobos/blob/master/std/traits.d#L6...
• Steven Schveighoffer (19/35) Oct 17 2021 `isIntegral` dates back to D1, where `__traits` didn't exist. The
• Andrei Alexandrescu (12/52) Oct 17 2021 Interesting, thanks. I saw there's plenty of other isXxx that differ
• Walter Bright (4/7) Oct 17 2021 More generally, "is a" and "is implicitly convertible to a" must be trea...
• Andrei Alexandrescu (2/4) Oct 17 2021 Word!
• Walter Bright (7/15) Oct 17 2021 I doubt I would have done one that was so different from the core langua...

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

According to https://github.com/dlang/phobos/blob/master/std/traits.d#L6191:

=====
Detect whether `T` is a built-in integral type. Types `bool`, `char`, 
`wchar`, and `dchar` are not considered integral.
=====

Not considered by whom? Certainly they are considered by the language 
per __traits(isIntegral). Also all conversion rules scream "they're 
integral!"

We even use the built-in trait to create a _different_ one!

Why do we have a slightly different with no added usabilty in the 
standard library?

Steven Schveighoffer <schveiguy gmail.com> writes:

On 10/17/21 10:36 AM, Andrei Alexandrescu wrote:
 According to 
 https://github.com/dlang/phobos/blob/master/std/traits.d#L6191:
 
 =====
 Detect whether `T` is a built-in integral type. Types `bool`, `char`, 
 `wchar`, and `dchar` are not considered integral.
 =====
 
 Not considered by whom? Certainly they are considered by the language 
 per __traits(isIntegral). Also all conversion rules scream "they're 
 integral!"
 
 We even use the built-in trait to create a _different_ one!
 
 Why do we have a slightly different with no added usabilty in the 
 standard library?

`isIntegral` dates back to D1, where `__traits` didn't exist. The 
current implementation is a "shorter" version of what was already there, 
without having to consider code breakage. This is the oldest thing I 
could find on github:

https://github.com/dlang/phobos/commit/eec6be69edec9601f9f856afcd25a797e845c181#diff-b7918b17cede734a2dd4ecbf2a981d597a5978f52e02f9a3c6f53c9abd797f05R322-R327

Note that this is an import from the old subversion repository, so 
attribution and PRs/etc. doesn't exist. You can keep looking on 
dsource.org if you want to find the original commit, but I'm almost 
positive it was Walter.

I think the original didn't include bool/[w|d]char either by 
carelessness or a belief that these things really shouldn't be integers 
(a great irony considering the contemporary pushback from Walter against 
splitting bool out from the integral family).

Things like this should have never been done, but now we have to live 
with it. Honestly, if we want to fix it, I would rather have the 
language enforce what std.traits says. So many problems happen by 
allowing e.g. integer promotion from `char` to `dchar`.

-Steve

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 10/17/21 11:07 AM, Steven Schveighoffer wrote:
 On 10/17/21 10:36 AM, Andrei Alexandrescu wrote:
 According to 
 https://github.com/dlang/phobos/blob/master/std/traits.d#L6191:

 =====
 Detect whether `T` is a built-in integral type. Types `bool`, `char`, 
 `wchar`, and `dchar` are not considered integral.
 =====

 Not considered by whom? Certainly they are considered by the language 
 per __traits(isIntegral). Also all conversion rules scream "they're 
 integral!"

 We even use the built-in trait to create a _different_ one!

 Why do we have a slightly different with no added usabilty in the 
 standard library?

 
 `isIntegral` dates back to D1, where `__traits` didn't exist. The 
 current implementation is a "shorter" version of what was already there, 
 without having to consider code breakage. This is the oldest thing I 
 could find on github:
 
 https://github.com/dlang/phobos/commit/eec6be69edec9601f9f856afcd25a797e845c181#diff-b7918b17cede734a2dd4ecbf2a981d597a5978f52e02f9a3c6f53
9abd797f05R322-R327 
 
 
 Note that this is an import from the old subversion repository, so 
 attribution and PRs/etc. doesn't exist. You can keep looking on 
 dsource.org if you want to find the original commit, but I'm almost 
 positive it was Walter.
 
 I think the original didn't include bool/[w|d]char either by 
 carelessness or a belief that these things really shouldn't be integers 
 (a great irony considering the contemporary pushback from Walter against 
 splitting bool out from the integral family).
 
 Things like this should have never been done, but now we have to live 
 with it. Honestly, if we want to fix it, I would rather have the 
 language enforce what std.traits says. So many problems happen by 
 allowing e.g. integer promotion from `char` to `dchar`.

Interesting, thanks. I saw there's plenty of other isXxx that differ 
from their built-in counterparts, perhaps with similar histories. I may 
have written some of that code.

As a pattern, I note just how complex the type system is and how many 
special cases there are:

* "alias this" shrapnel is all over the place. We should simply state 
that phobos does not support "alias this" at all. Do conversions on the 
call side.

* __vector just sticks its nose in random places.

* There's a lot of effort to legitimize enum as a seamless part of the 
type system - sadly it's not seamless at all.

Walter Bright <newshound2 digitalmars.com> writes:

On 10/17/2021 12:19 PM, Andrei Alexandrescu wrote:
 As a pattern, I note just how complex the type system is and how many special 
 cases there are:

and:

 Do conversions on the call side.

More generally, "is a" and "is implicitly convertible to a" must be treated 
distinctly as separate operations.

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 10/17/21 8:13 PM, Walter Bright wrote:
 More generally, "is a" and "is implicitly convertible to a" must be 
 treated distinctly as separate operations.

Word!

Walter Bright <newshound2 digitalmars.com> writes:

On 10/17/2021 8:07 AM, Steven Schveighoffer wrote:
 Note that this is an import from the old subversion repository, so attribution 
 and PRs/etc. doesn't exist. You can keep looking on dsource.org if you want to 
 find the original commit, but I'm almost positive it was Walter.
 
 I think the original didn't include bool/[w|d]char either by carelessness or a 
 belief that these things really shouldn't be integers (a great irony
considering 
 the contemporary pushback from Walter against splitting bool out from the 
 integral family).

I doubt I would have done one that was so different from the core language's 
view of an integral type, though of course I can't prove it.

Keep in mind that D1's library largely consisted of work done by people other 
than me, and a lot was done without a lot of review by me.

You're right that it's far too late to fix this. Hence the purpose behind a 
Phobos v2.