On Sat, Aug 27, 2022 at 11:21 AM Михаил Найденов via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> Hello again,
> I ended up writing a small proposal on this topic as I am quite bothered
> with the issue.
> Attached is the draft
>

Hi Mikhail,
I looked at your paper. I think it needs to use the words "concept maps"
somewhere in the paper: that's basically what you're proposing as a
solution, but the paper doesn't show any evidence that you've dug into the
previous proposals and why they failed.

Then, at a higher level, you have not convinced me that there's any problem
here at all! Your original, "just programming," version of your function
looks like this (quote):

void silly(string& s)
<https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=aba66a32fc&attid=0.1&permmsgid=msg-f:1742328244751920533&th=182dfe4eae916d95&view=att&disp=inline&realattid=f_l7c1rr8i0&ser=1&saddbat=ANGjdJ_qVCrD5VtcwzbDcbDVeAnx9f6fofNi6MFWBJgCz-kQlYEx_Pci4UMbG80BfeZubUoYMz555AJPQ_GQrjr1ylClW6FqsctQ_q9XwxnECGc81qd5v9ZsHPBye9abZ-z7F7s332ZLrcB7CqT6cVZ1BQ9yCdbUq_emtRQoW08fcluey9zkq9TpCjACPnHj69Kj3ykd0TDz3R_IQSMVrbVu2zG1SqoLnMr0I5IpP_0zdYFUMc5KirVALGeMo2YEX88TwkuGnNreTra-tRooWHcf75Kyc4vKrW4Ym8y22tNpMsTABG7cL6eRiIwS03xUXiyTrUrbhv8rm42IQ22TU9ksCz8NqnLGMoiAdoeh1kxGPQtHPZM6QKWr-m19Gi-wZcnhpF-jiO6_U8t9meAQ6LxERVXj7oDZbSrEtH7C99YSbe_qBEWYCnIWFNMvd5LmsCagaWKn_QdXj_sp9i9sprmVhjRCWaW3uDgNYCE0dZnsLfec2uUAtbtytxYnk5oGjEXHtJuTyT7QUsac3aEijECz-dY79EmgkE1FP5cPKDsW1JKEceyBSTf5ES29BJD_xSeFNsyzJulgeMSVjCbjke_nNQENVy7MBDD-mwuYLlkqraCHGZkh1Oo1eXjuQkK3koa0So6EKZjlwH3WtZHuVGX9XAzsaNErvuuHRo9QelEMU7l5FMQd2dO93rPwyXPGl__2bKexc-3hvoaSs9Kz5uTp-Q30iuSXJdU2bGxqzbLzq_BQy1aag6nmNdCS3oaRWHL37rMT6fsu6K9ZHlQgcpNjujVwfkACKWiGIAWWVKZif3wx7Mppek2ApXWZKZr9A1ZtiwE7z9e7TRfq2U2X#m__cb1-3>{
<https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=aba66a32fc&attid=0.1&permmsgid=msg-f:1742328244751920533&th=182dfe4eae916d95&view=att&disp=inline&realattid=f_l7c1rr8i0&ser=1&saddbat=ANGjdJ_qVCrD5VtcwzbDcbDVeAnx9f6fofNi6MFWBJgCz-kQlYEx_Pci4UMbG80BfeZubUoYMz555AJPQ_GQrjr1ylClW6FqsctQ_q9XwxnECGc81qd5v9ZsHPBye9abZ-z7F7s332ZLrcB7CqT6cVZ1BQ9yCdbUq_emtRQoW08fcluey9zkq9TpCjACPnHj69Kj3ykd0TDz3R_IQSMVrbVu2zG1SqoLnMr0I5IpP_0zdYFUMc5KirVALGeMo2YEX88TwkuGnNreTra-tRooWHcf75Kyc4vKrW4Ym8y22tNpMsTABG7cL6eRiIwS03xUXiyTrUrbhv8rm42IQ22TU9ksCz8NqnLGMoiAdoeh1kxGPQtHPZM6QKWr-m19Gi-wZcnhpF-jiO6_U8t9meAQ6LxERVXj7oDZbSrEtH7C99YSbe_qBEWYCnIWFNMvd5LmsCagaWKn_QdXj_sp9i9sprmVhjRCWaW3uDgNYCE0dZnsLfec2uUAtbtytxYnk5oGjEXHtJuTyT7QUsac3aEijECz-dY79EmgkE1FP5cPKDsW1JKEceyBSTf5ES29BJD_xSeFNsyzJulgeMSVjCbjke_nNQENVy7MBDD-mwuYLlkqraCHGZkh1Oo1eXjuQkK3koa0So6EKZjlwH3WtZHuVGX9XAzsaNErvuuHRo9QelEMU7l5FMQd2dO93rPwyXPGl__2bKexc-3hvoaSs9Kz5uTp-Q30iuSXJdU2bGxqzbLzq_BQy1aag6nmNdCS3oaRWHL37rMT6fsu6K9ZHlQgcpNjujVwfkACKWiGIAWWVKZif3wx7Mppek2ApXWZKZr9A1ZtiwE7z9e7TRfq2U2X#m__cb1-4>
 using char_type = string::char_type;
<https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=aba66a32fc&attid=0.1&permmsgid=msg-f:1742328244751920533&th=182dfe4eae916d95&view=att&disp=inline&realattid=f_l7c1rr8i0&ser=1&saddbat=ANGjdJ_qVCrD5VtcwzbDcbDVeAnx9f6fofNi6MFWBJgCz-kQlYEx_Pci4UMbG80BfeZubUoYMz555AJPQ_GQrjr1ylClW6FqsctQ_q9XwxnECGc81qd5v9ZsHPBye9abZ-z7F7s332ZLrcB7CqT6cVZ1BQ9yCdbUq_emtRQoW08fcluey9zkq9TpCjACPnHj69Kj3ykd0TDz3R_IQSMVrbVu2zG1SqoLnMr0I5IpP_0zdYFUMc5KirVALGeMo2YEX88TwkuGnNreTra-tRooWHcf75Kyc4vKrW4Ym8y22tNpMsTABG7cL6eRiIwS03xUXiyTrUrbhv8rm42IQ22TU9ksCz8NqnLGMoiAdoeh1kxGPQtHPZM6QKWr-m19Gi-wZcnhpF-jiO6_U8t9meAQ6LxERVXj7oDZbSrEtH7C99YSbe_qBEWYCnIWFNMvd5LmsCagaWKn_QdXj_sp9i9sprmVhjRCWaW3uDgNYCE0dZnsLfec2uUAtbtytxYnk5oGjEXHtJuTyT7QUsac3aEijECz-dY79EmgkE1FP5cPKDsW1JKEceyBSTf5ES29BJD_xSeFNsyzJulgeMSVjCbjke_nNQENVy7MBDD-mwuYLlkqraCHGZkh1Oo1eXjuQkK3koa0So6EKZjlwH3WtZHuVGX9XAzsaNErvuuHRo9QelEMU7l5FMQd2dO93rPwyXPGl__2bKexc-3hvoaSs9Kz5uTp-Q30iuSXJdU2bGxqzbLzq_BQy1aag6nmNdCS3oaRWHL37rMT6fsu6K9ZHlQgcpNjujVwfkACKWiGIAWWVKZif3wx7Mppek2ApXWZKZr9A1ZtiwE7z9e7TRfq2U2X#m__cb1-5>
 // ... <https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=aba66a32fc&attid=0.1&permmsgid=msg-f:1742328244751920533&th=182dfe4eae916d95&view=att&disp=inline&realattid=f_l7c1rr8i0&ser=1&saddbat=ANGjdJ_qVCrD5VtcwzbDcbDVeAnx9f6fofNi6MFWBJgCz-kQlYEx_Pci4UMbG80BfeZubUoYMz555AJPQ_GQrjr1ylClW6FqsctQ_q9XwxnECGc81qd5v9ZsHPBye9abZ-z7F7s332ZLrcB7CqT6cVZ1BQ9yCdbUq_emtRQoW08fcluey9zkq9TpCjACPnHj69Kj3ykd0TDz3R_IQSMVrbVu2zG1SqoLnMr0I5IpP_0zdYFUMc5KirVALGeMo2YEX88TwkuGnNreTra-tRooWHcf75Kyc4vKrW4Ym8y22tNpMsTABG7cL6eRiIwS03xUXiyTrUrbhv8rm42IQ22TU9ksCz8NqnLGMoiAdoeh1kxGPQtHPZM6QKWr-m19Gi-wZcnhpF-jiO6_U8t9meAQ6LxERVXj7oDZbSrEtH7C99YSbe_qBEWYCnIWFNMvd5LmsCagaWKn_QdXj_sp9i9sprmVhjRCWaW3uDgNYCE0dZnsLfec2uUAtbtytxYnk5oGjEXHtJuTyT7QUsac3aEijECz-dY79EmgkE1FP5cPKDsW1JKEceyBSTf5ES29BJD_xSeFNsyzJulgeMSVjCbjke_nNQENVy7MBDD-mwuYLlkqraCHGZkh1Oo1eXjuQkK3koa0So6EKZjlwH3WtZHuVGX9XAzsaNErvuuHRo9QelEMU7l5FMQd2dO93rPwyXPGl__2bKexc-3hvoaSs9Kz5uTp-Q30iuSXJdU2bGxqzbLzq_BQy1aag6nmNdCS3oaRWHL37rMT6fsu6K9ZHlQgcpNjujVwfkACKWiGIAWWVKZif3wx7Mppek2ApXWZKZr9A1ZtiwE7z9e7TRfq2U2X#m__cb1-6>
 if(s.starts_with("hello"))
<https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=aba66a32fc&attid=0.1&permmsgid=msg-f:1742328244751920533&th=182dfe4eae916d95&view=att&disp=inline&realattid=f_l7c1rr8i0&ser=1&saddbat=ANGjdJ_qVCrD5VtcwzbDcbDVeAnx9f6fofNi6MFWBJgCz-kQlYEx_Pci4UMbG80BfeZubUoYMz555AJPQ_GQrjr1ylClW6FqsctQ_q9XwxnECGc81qd5v9ZsHPBye9abZ-z7F7s332ZLrcB7CqT6cVZ1BQ9yCdbUq_emtRQoW08fcluey9zkq9TpCjACPnHj69Kj3ykd0TDz3R_IQSMVrbVu2zG1SqoLnMr0I5IpP_0zdYFUMc5KirVALGeMo2YEX88TwkuGnNreTra-tRooWHcf75Kyc4vKrW4Ym8y22tNpMsTABG7cL6eRiIwS03xUXiyTrUrbhv8rm42IQ22TU9ksCz8NqnLGMoiAdoeh1kxGPQtHPZM6QKWr-m19Gi-wZcnhpF-jiO6_U8t9meAQ6LxERVXj7oDZbSrEtH7C99YSbe_qBEWYCnIWFNMvd5LmsCagaWKn_QdXj_sp9i9sprmVhjRCWaW3uDgNYCE0dZnsLfec2uUAtbtytxYnk5oGjEXHtJuTyT7QUsac3aEijECz-dY79EmgkE1FP5cPKDsW1JKEceyBSTf5ES29BJD_xSeFNsyzJulgeMSVjCbjke_nNQENVy7MBDD-mwuYLlkqraCHGZkh1Oo1eXjuQkK3koa0So6EKZjlwH3WtZHuVGX9XAzsaNErvuuHRo9QelEMU7l5FMQd2dO93rPwyXPGl__2bKexc-3hvoaSs9Kz5uTp-Q30iuSXJdU2bGxqzbLzq_BQy1aag6nmNdCS3oaRWHL37rMT6fsu6K9ZHlQgcpNjujVwfkACKWiGIAWWVKZif3wx7Mppek2ApXWZKZr9A1ZtiwE7z9e7TRfq2U2X#m__cb1-7>
    s.clear(); <https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=aba66a32fc&attid=0.1&permmsgid=msg-f:1742328244751920533&th=182dfe4eae916d95&view=att&disp=inline&realattid=f_l7c1rr8i0&ser=1&saddbat=ANGjdJ_qVCrD5VtcwzbDcbDVeAnx9f6fofNi6MFWBJgCz-kQlYEx_Pci4UMbG80BfeZubUoYMz555AJPQ_GQrjr1ylClW6FqsctQ_q9XwxnECGc81qd5v9ZsHPBye9abZ-z7F7s332ZLrcB7CqT6cVZ1BQ9yCdbUq_emtRQoW08fcluey9zkq9TpCjACPnHj69Kj3ykd0TDz3R_IQSMVrbVu2zG1SqoLnMr0I5IpP_0zdYFUMc5KirVALGeMo2YEX88TwkuGnNreTra-tRooWHcf75Kyc4vKrW4Ym8y22tNpMsTABG7cL6eRiIwS03xUXiyTrUrbhv8rm42IQ22TU9ksCz8NqnLGMoiAdoeh1kxGPQtHPZM6QKWr-m19Gi-wZcnhpF-jiO6_U8t9meAQ6LxERVXj7oDZbSrEtH7C99YSbe_qBEWYCnIWFNMvd5LmsCagaWKn_QdXj_sp9i9sprmVhjRCWaW3uDgNYCE0dZnsLfec2uUAtbtytxYnk5oGjEXHtJuTyT7QUsac3aEijECz-dY79EmgkE1FP5cPKDsW1JKEceyBSTf5ES29BJD_xSeFNsyzJulgeMSVjCbjke_nNQENVy7MBDD-mwuYLlkqraCHGZkh1Oo1eXjuQkK3koa0So6EKZjlwH3WtZHuVGX9XAzsaNErvuuHRo9QelEMU7l5FMQd2dO93rPwyXPGl__2bKexc-3hvoaSs9Kz5uTp-Q30iuSXJdU2bGxqzbLzq_BQy1aag6nmNdCS3oaRWHL37rMT6fsu6K9ZHlQgcpNjujVwfkACKWiGIAWWVKZif3wx7Mppek2ApXWZKZr9A1ZtiwE7z9e7TRfq2U2X#m__cb1-8>
 // ... <https://mail-attachment.googleusercontent.com/attachment/u/0/?ui=2&ik=aba66a32fc&attid=0.1&permmsgid=msg-f:1742328244751920533&th=182dfe4eae916d95&view=att&disp=inline&realattid=f_l7c1rr8i0&ser=1&saddbat=ANGjdJ_qVCrD5VtcwzbDcbDVeAnx9f6fofNi6MFWBJgCz-kQlYEx_Pci4UMbG80BfeZubUoYMz555AJPQ_GQrjr1ylClW6FqsctQ_q9XwxnECGc81qd5v9ZsHPBye9abZ-z7F7s332ZLrcB7CqT6cVZ1BQ9yCdbUq_emtRQoW08fcluey9zkq9TpCjACPnHj69Kj3ykd0TDz3R_IQSMVrbVu2zG1SqoLnMr0I5IpP_0zdYFUMc5KirVALGeMo2YEX88TwkuGnNreTra-tRooWHcf75Kyc4vKrW4Ym8y22tNpMsTABG7cL6eRiIwS03xUXiyTrUrbhv8rm42IQ22TU9ksCz8NqnLGMoiAdoeh1kxGPQtHPZM6QKWr-m19Gi-wZcnhpF-jiO6_U8t9meAQ6LxERVXj7oDZbSrEtH7C99YSbe_qBEWYCnIWFNMvd5LmsCagaWKn_QdXj_sp9i9sprmVhjRCWaW3uDgNYCE0dZnsLfec2uUAtbtytxYnk5oGjEXHtJuTyT7QUsac3aEijECz-dY79EmgkE1FP5cPKDsW1JKEceyBSTf5ES29BJD_xSeFNsyzJulgeMSVjCbjke_nNQENVy7MBDD-mwuYLlkqraCHGZkh1Oo1eXjuQkK3koa0So6EKZjlwH3WtZHuVGX9XAzsaNErvuuHRo9QelEMU7l5FMQd2dO93rPwyXPGl__2bKexc-3hvoaSs9Kz5uTp-Q30iuSXJdU2bGxqzbLzq_BQy1aag6nmNdCS3oaRWHL37rMT6fsu6K9ZHlQgcpNjujVwfkACKWiGIAWWVKZif3wx7Mppek2ApXWZKZr9A1ZtiwE7z9e7TRfq2U2X#m__cb1-9>}

I don't think that code is ordinary "just programming" at all!
`std::string::char_type` (1) does not exist, and (2) even if it did exist,
I assume it would be an unnecessarily verbose way of spelling "char". So
let's eliminate that line. Then, we're left with nicely* generic *code,
that looks just like classic Stepanov STL code. This function template (or
"algorithm") can be compiled and works perfectly for any concrete type that
implements the `starts_with` method (e.g. `string`, `string_view`) and the
`clear` method (e.g. `string`, `vector`, `deque`, `map`, `set`...)

template<class T>
void silly(T& t) {
    if (t.starts_with("hello")) t.clear();
}

Of course in the actual STL there's only the one type (`string`) that
supports both of those operations. But that's fine, because that's the only
STL type that can actually be used with this template. If we intended to
use it with both `string` and `string_view`, we could generalize it a
little further like this:

template<class T>
void silly(T& t) {
    if (t.starts_with("hello")) t = T();
}

But nobody writes templates in a vacuum: there's always some actual
business purpose behind writing the template. Usually it's to avoid code
duplication: we have two or more *known* types that satisfy the same
interface, and so we can write one ("statically polymorphic") version of
our algorithm using a template like `silly`. The interface and the template
algorithm generally will evolve cooperatively. For example, the STL is
designed to facilitate the writing of algorithms that work for any kind of
STL container, so, all STL containers support the same vocabulary of
methods: `insert`, `erase`, `begin`, `end`, `T::iterator`, `T::value_type`,
and so on.

It seems to me that you're identifying the problem as "I can't write a
template that works for *all possible types*, because
(statically-)polymorphic code implies an interface, and not every possible
type will implement the interface I require." But that's not a real-world
problem, because in the real world we don't write code to work with *every
possible type*. And then, you have an XY problem: you try to get around
this artificial problem by crufting up your code, turning all your methods
into free functions and adding a lot of `::`s, and then complain that this
makes the code uglier. Yes — but that's the "Y" problem! Crufting up the
code is ugly, but it isn't necessary to solve your "X" problem; and in
fact, it's not even *sufficient*. In order to use polymorphism (*either*
static polymorphism with templates, *or* classical runtime polymorphism
with inheritance), your types must conform to some kind of interface.
That's both unavoidable and beneficial-to-the-reader.

my $.02,
Arthur