Date: Wed, 14 Jul 2021 07:55:44 +0200 (CEST)
ok, thanks. jerry
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Message: 1
Date: Tue, 13 Jul 2021 22:28:12 +0200
From: Antoine Viallon <antoine_at_[hidden]>
To: std-proposals_at_[hidden]
Subject: Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
Message-ID: <A3A6CD11-1AC6-42BA-8767-87A5E26E70D1_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
Why isn't it fitting?
The only language change would be to allow it to be used in casting
parameters.
And yes, it stores a runtime representation of a type.
Actually, typeof returns an object of type type_info.
Antoine Viallon
-------- Courriel d?origine --------
De?: Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
Envoy??: 13 juillet 2021 20:17:24 GMT+02:00
??: std-proposals_at_[hidden]
Cc?: Jaroslav Moravec <j.moravec.email_at_[hidden]>
Objet?: Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
To understand what I need:
I need the type-casting to be "run-time" process.
Understand me ?
Jerry
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run-time type-cast operations (Antoine Viallon)
2. Re: a new proposal. (Ga?per A?man)
----------------------------------------------------------------------
Message: 1
Date: Tue, 13 Jul 2021 15:01:31 +0200
From: Antoine Viallon <antoine_at_[hidden]>
To: std-proposals_at_[hidden]
Subject: Re: [std-proposals] A new proposal, new key-word definition
for dynamic, run-time type-cast operations
Message-ID: <79FA6351-C0A4-4A70-9C28-73FD3C87341F_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
Hello,
I quickly read what you sent,
And I have a question:
Isn't there a "typeinfo" header containing something able to hold type
information? There is typeindex also, if I'm not mistaken.
Maybe the only thing you need is to be able to use such types in a dynamic_
cast
In any case, I see a very useful use-case for an argument parser for
instance.
Antoine Viallon
-------- Courriel d?origine --------
De?: Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
Envoy??: 13 juillet 2021 14:44:50 GMT+02:00
??: std-proposals_at_[hidden]
Cc?: Jaroslav Moravec <j.moravec.email_at_[hidden]>
Objet?: [std-proposals] A new proposal, new key-word definition for dynamic,
run-time type-cast operations
New proposal, version 2.
Abstract
The C++ language is here for more that 36 years and is still under
development. Sometimes, C++ borrows some ideas from other programming
languages, sometimes works on its own way. Presented proposal try to
introduce a new type of basic variable which would be capable to hold a type
of a variable or a type of a class or a struct. This variable should be
capable to define target new type in type-cast operations such us: static_
cast or dynamic_cast etc. Both at running time and at compilation time. Type
of a variable or a class/struct is usually given by its unique name. Thus,
the new basic variable should contain a string ? the name of basic datatype
or a type of user defined datatype. This name is then used in the type-cast
operation at running time. The target type is, of course, well known at
compilation time.
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Message: 2
Date: Tue, 13 Jul 2021 17:42:32 +0100
From: Ga?per A?man <gasper.azman_at_[hidden]>
To: Std-Proposals <std-proposals_at_[hidden]>
Subject: Re: [std-proposals] a new proposal.
Message-ID:
<CAANG=kUPxVURJhCJFqzYWRhsxDv6_Fz0rrbavj091d3OXvz71Q_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
the dynamic_cast to a type-id is a really interesting call-site syntax for
open multimethods - the problem isn't that this hasn't been tried (just
look for multimethods) - the problem is we don't know of an efficient and
correct way to implement the dispatch tables.
If you are forced to write the switch statement based on the type-index
yourself, then at least you need to list, exhaustively, the types you care
about. Pattern matching is another way to do this. I'm not sure your
proposal is implementable.
G
On Tue, Jul 13, 2021 at 11:26 AM Marcin Jaczewski via Std-Proposals <
std-proposals_at_[hidden]> wrote:
> I look like `dynamic` form C# but this mean it relay on reflection to
> work correctly:
> ```c#
> dynamic d = x;
> int i = d.item;
> ```
> is equal to
> ```c#
> DynamicType d = new DynamicType(x);
> int i = (int)d["item"];
> ```
> C++ could have static reflection but this requires dynamic reflection
> to work (static could generate dynamic but it will be costly).
> Another thing is dynamic code generation other wise you can't have code
> like:
>
> ```c++
> std::cout << declarative_cast<type_var>(var);
> ```
> where type can be `int`, `long` or `std::vector<int>` and all need
> have its own `<<` that is templated function that usually is inlined.
> Does this mean `type_var` needs to store all possible template functions?
>
> Beside syntax like `declarative_cast<arg[0]->i>` is wrong as it mix
> compile time template arguments with runtime arguments, something only
> could work
> if you use constexpr variables but it's not something your example wants
> to do.
>
>
> Lot better would expand `std::any` and allow easy way to have multiple
> type callbacks like:
> ```c++
> std::any z = 17;
>
> vist_any<int, long, std::vector<int>>(z, [](auto& w) { std::cout <<
> w; }); //you need name all types you want use
> ```
> and this is possible even if C++14
>
> wt., 13 lip 2021 o 11:27 Jaroslav Moravec via Std-Proposals
> <std-proposals_at_[hidden]> napisa?(a):
> >
> > The proposal is in attachments. --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden]
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> --
> Std-Proposals mailing list
> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>
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Message: 2
Date: Tue, 13 Jul 2021 21:50:24 +0100
From: Ga?per A?man <gasper.azman_at_[hidden]>
To: Std-Proposals <std-proposals_at_[hidden]>
Subject: Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
Message-ID:
<CAANG=kWG7NJ57BfZC1Xw5frB6SmWE81V8pMVmGzknGMHbBTemw_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
What is the static type of that expression? How do you do overload
resolution, for every possible grammar production that includes it?
On Tue, Jul 13, 2021, 21:29 Antoine Viallon via Std-Proposals <
std-proposals_at_[hidden]> wrote:
> Why isn't it fitting?
> The only language change would be to allow it to be used in casting
> parameters.
> And yes, it stores a runtime representation of a type.
> Actually, typeof returns an object of type type_info.
>
> Antoine Viallon
>
> ------------------------------
> *De :* Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
> *Envoy? :* 13 juillet 2021 20:17:24 GMT+02:00
> *? :* std-proposals_at_[hidden]
> *Cc :* Jaroslav Moravec <j.moravec.email_at_[hidden]>
> *Objet :* Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
>
> To understand what I need:
>
> I need the type-casting to be "run-time" process.
> Understand me ?
>
> Jerry
>
> ---------- P?vodn? e-mail ----------
> Od: std-proposals-request_at_[hidden]
> Komu: std-proposals_at_[hidden]
> Datum: 13. 7. 2021 19:01:01
> P?edm?t: Std-Proposals Digest, Vol 28, Issue 27
>
> Send Std-Proposals mailing list submissions to
> std-proposals_at_[hidden]
>
> To subscribe or unsubscribe via the World Wide Web, visit
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> or, via email, send a message with subject or body 'help' to
> std-proposals-request_at_[hidden]
>
> You can reach the person managing the list at
> std-proposals-owner_at_[hidden]
>
> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of Std-Proposals digest..."
>
>
> Today's Topics:
>
> 1. Re: A new proposal, new key-word definition for dynamic,
> run-time type-cast operations (Antoine Viallon)
> 2. Re: a new proposal. (Ga?per A?man)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 13 Jul 2021 15:01:31 +0200
> From: Antoine Viallon <antoine_at_[hidden]>
> To: std-proposals_at_[hidden]
> Subject: Re: [std-proposals] A new proposal, new key-word definition
> for dynamic, run-time type-cast operations
> Message-ID: <79FA6351-C0A4-4A70-9C28-73FD3C87341F_at_[hidden]>
> Content-Type: text/plain; charset="utf-8"
>
> Hello,
> I quickly read what you sent,
> And I have a question:
> Isn't there a "typeinfo" header containing something able to hold type
> information? There is typeindex also, if I'm not mistaken.
> Maybe the only thing you need is to be able to use such types in a
> dynamic_cast
>
> In any case, I see a very useful use-case for an argument parser for
> instance.
>
> Antoine Viallon
>
>
> -------- Courriel d?origine --------
> De?: Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
> Envoy??: 13 juillet 2021 14:44:50 GMT+02:00
> ??: std-proposals_at_[hidden]
> Cc?: Jaroslav Moravec <j.moravec.email_at_[hidden]>
> Objet?: [std-proposals] A new proposal, new key-word definition for
> dynamic, run-time type-cast operations
>
>
> New proposal, version 2.
>
>
>
>
>
> Abstract
>
>
>
> The C++ language is here for more that 36 years and is still under
> development. Sometimes, C++ borrows some ideas from other programming
> languages, sometimes works on its own way. Presented proposal try to
> introduce a new type of basic variable which would be capable to hold a
> type
> of a variable or a type of a class or a struct. This variable should be
> capable to define target new type in type-cast operations such us: static_
> cast or dynamic_cast etc. Both at running time and at compilation time.
> Type
> of a variable or a class/struct is usually given by its unique name. Thus,
> the new basic variable should contain a string ? the name of basic
> datatype
> or a type of user defined datatype. This name is then used in the
> type-cast
> operation at running time. The target type is, of course, well known at
> compilation time.
> -------------- next part --------------
> HTML attachment scrubbed and removed
>
> ------------------------------
>
> Message: 2
> Date: Tue, 13 Jul 2021 17:42:32 +0100
> From: Ga?per A?man <gasper.azman_at_[hidden]>
> To: Std-Proposals <std-proposals_at_[hidden]>
> Subject: Re: [std-proposals] a new proposal.
> Message-ID:
> <CAANG=kUPxVURJhCJFqzYWRhsxDv6_Fz0rrbavj091d3OXvz71Q_at_[hidden]>
> Content-Type: text/plain; charset="utf-8"
>
> the dynamic_cast to a type-id is a really interesting call-site syntax for
> open multimethods - the problem isn't that this hasn't been tried (just
> look for multimethods) - the problem is we don't know of an efficient and
> correct way to implement the dispatch tables.
>
> If you are forced to write the switch statement based on the type-index
> yourself, then at least you need to list, exhaustively, the types you care
> about. Pattern matching is another way to do this. I'm not sure your
> proposal is implementable.
>
> G
>
> On Tue, Jul 13, 2021 at 11:26 AM Marcin Jaczewski via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
> > I look like `dynamic` form C# but this mean it relay on reflection to
> > work correctly:
> > ```c#
> > dynamic d = x;
> > int i = d.item;
> > ```
> > is equal to
> > ```c#
> > DynamicType d = new DynamicType(x);
> > int i = (int)d["item"];
> > ```
> > C++ could have static reflection but this requires dynamic reflection
> > to work (static could generate dynamic but it will be costly).
> > Another thing is dynamic code generation other wise you can't have code
> > like:
> >
> > ```c++
> > std::cout << declarative_cast<type_var>(var);
> > ```
> > where type can be `int`, `long` or `std::vector<int>` and all need
> > have its own `<<` that is templated function that usually is inlined.
> > Does this mean `type_var` needs to store all possible template
> functions?
> >
> > Beside syntax like `declarative_cast<arg[0]->i>` is wrong as it mix
> > compile time template arguments with runtime arguments, something only
> > could work
> > if you use constexpr variables but it's not something your example wants
> > to do.
> >
> >
> > Lot better would expand `std::any` and allow easy way to have multiple
> > type callbacks like:
> > ```c++
> > std::any z = 17;
> >
> > vist_any<int, long, std::vector<int>>(z, [](auto& w) { std::cout <<
> > w; }); //you need name all types you want use
> > ```
> > and this is possible even if C++14
> >
> > wt., 13 lip 2021 o 11:27 Jaroslav Moravec via Std-Proposals
> > <std-proposals_at_[hidden]> napisa?(a):
> > >
> > > The proposal is in attachments. --
> > > Std-Proposals mailing list
> > > Std-Proposals_at_[hidden]
> > > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> > --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden]
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> >
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2. Re: Std-Proposals Digest, Vol 28, Issue 27 (Ga?per A?man)
----------------------------------------------------------------------
Message: 1
Date: Tue, 13 Jul 2021 22:28:12 +0200
From: Antoine Viallon <antoine_at_[hidden]>
To: std-proposals_at_[hidden]
Subject: Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
Message-ID: <A3A6CD11-1AC6-42BA-8767-87A5E26E70D1_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
Why isn't it fitting?
The only language change would be to allow it to be used in casting
parameters.
And yes, it stores a runtime representation of a type.
Actually, typeof returns an object of type type_info.
Antoine Viallon
-------- Courriel d?origine --------
De?: Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
Envoy??: 13 juillet 2021 20:17:24 GMT+02:00
??: std-proposals_at_[hidden]
Cc?: Jaroslav Moravec <j.moravec.email_at_[hidden]>
Objet?: Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
To understand what I need:
I need the type-casting to be "run-time" process.
Understand me ?
Jerry
---------- P?vodn? e-mail ----------
Od: std-proposals-request_at_[hidden]
Komu: std-proposals_at_[hidden]
Datum: 13. 7. 2021 19:01:01
P?edm?t: Std-Proposals Digest, Vol 28, Issue 27
"Send Std-Proposals mailing list submissions to
std-proposals_at_[hidden]
To subscribe or unsubscribe via the World Wide Web, visit
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Today's Topics:
1. Re: A new proposal, new key-word definition for dynamic,
run-time type-cast operations (Antoine Viallon)
2. Re: a new proposal. (Ga?per A?man)
----------------------------------------------------------------------
Message: 1
Date: Tue, 13 Jul 2021 15:01:31 +0200
From: Antoine Viallon <antoine_at_[hidden]>
To: std-proposals_at_[hidden]
Subject: Re: [std-proposals] A new proposal, new key-word definition
for dynamic, run-time type-cast operations
Message-ID: <79FA6351-C0A4-4A70-9C28-73FD3C87341F_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
Hello,
I quickly read what you sent,
And I have a question:
Isn't there a "typeinfo" header containing something able to hold type
information? There is typeindex also, if I'm not mistaken.
Maybe the only thing you need is to be able to use such types in a dynamic_
cast
In any case, I see a very useful use-case for an argument parser for
instance.
Antoine Viallon
-------- Courriel d?origine --------
De?: Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
Envoy??: 13 juillet 2021 14:44:50 GMT+02:00
??: std-proposals_at_[hidden]
Cc?: Jaroslav Moravec <j.moravec.email_at_[hidden]>
Objet?: [std-proposals] A new proposal, new key-word definition for dynamic,
run-time type-cast operations
New proposal, version 2.
Abstract
The C++ language is here for more that 36 years and is still under
development. Sometimes, C++ borrows some ideas from other programming
languages, sometimes works on its own way. Presented proposal try to
introduce a new type of basic variable which would be capable to hold a type
of a variable or a type of a class or a struct. This variable should be
capable to define target new type in type-cast operations such us: static_
cast or dynamic_cast etc. Both at running time and at compilation time. Type
of a variable or a class/struct is usually given by its unique name. Thus,
the new basic variable should contain a string ? the name of basic datatype
or a type of user defined datatype. This name is then used in the type-cast
operation at running time. The target type is, of course, well known at
compilation time.
-------------- next part --------------
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------------------------------
Message: 2
Date: Tue, 13 Jul 2021 17:42:32 +0100
From: Ga?per A?man <gasper.azman_at_[hidden]>
To: Std-Proposals <std-proposals_at_[hidden]>
Subject: Re: [std-proposals] a new proposal.
Message-ID:
<CAANG=kUPxVURJhCJFqzYWRhsxDv6_Fz0rrbavj091d3OXvz71Q_at_[hidden]>
Content-Type: text/plain; charset="utf-8"
the dynamic_cast to a type-id is a really interesting call-site syntax for
open multimethods - the problem isn't that this hasn't been tried (just
look for multimethods) - the problem is we don't know of an efficient and
correct way to implement the dispatch tables.
If you are forced to write the switch statement based on the type-index
yourself, then at least you need to list, exhaustively, the types you care
about. Pattern matching is another way to do this. I'm not sure your
proposal is implementable.
G
On Tue, Jul 13, 2021 at 11:26 AM Marcin Jaczewski via Std-Proposals <
std-proposals_at_[hidden]> wrote:
> I look like `dynamic` form C# but this mean it relay on reflection to
> work correctly:
> ```c#
> dynamic d = x;
> int i = d.item;
> ```
> is equal to
> ```c#
> DynamicType d = new DynamicType(x);
> int i = (int)d["item"];
> ```
> C++ could have static reflection but this requires dynamic reflection
> to work (static could generate dynamic but it will be costly).
> Another thing is dynamic code generation other wise you can't have code
> like:
>
> ```c++
> std::cout << declarative_cast<type_var>(var);
> ```
> where type can be `int`, `long` or `std::vector<int>` and all need
> have its own `<<` that is templated function that usually is inlined.
> Does this mean `type_var` needs to store all possible template functions?
>
> Beside syntax like `declarative_cast<arg[0]->i>` is wrong as it mix
> compile time template arguments with runtime arguments, something only
> could work
> if you use constexpr variables but it's not something your example wants
> to do.
>
>
> Lot better would expand `std::any` and allow easy way to have multiple
> type callbacks like:
> ```c++
> std::any z = 17;
>
> vist_any<int, long, std::vector<int>>(z, [](auto& w) { std::cout <<
> w; }); //you need name all types you want use
> ```
> and this is possible even if C++14
>
> wt., 13 lip 2021 o 11:27 Jaroslav Moravec via Std-Proposals
> <std-proposals_at_[hidden]> napisa?(a):
> >
> > The proposal is in attachments. --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden]
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> --
> Std-Proposals mailing list
> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
>
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Message: 2
Date: Tue, 13 Jul 2021 21:50:24 +0100
From: Ga?per A?man <gasper.azman_at_[hidden]>
To: Std-Proposals <std-proposals_at_[hidden]>
Subject: Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
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What is the static type of that expression? How do you do overload
resolution, for every possible grammar production that includes it?
On Tue, Jul 13, 2021, 21:29 Antoine Viallon via Std-Proposals <
std-proposals_at_[hidden]> wrote:
> Why isn't it fitting?
> The only language change would be to allow it to be used in casting
> parameters.
> And yes, it stores a runtime representation of a type.
> Actually, typeof returns an object of type type_info.
>
> Antoine Viallon
>
> ------------------------------
> *De :* Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
> *Envoy? :* 13 juillet 2021 20:17:24 GMT+02:00
> *? :* std-proposals_at_[hidden]
> *Cc :* Jaroslav Moravec <j.moravec.email_at_[hidden]>
> *Objet :* Re: [std-proposals] Std-Proposals Digest, Vol 28, Issue 27
>
> To understand what I need:
>
> I need the type-casting to be "run-time" process.
> Understand me ?
>
> Jerry
>
> ---------- P?vodn? e-mail ----------
> Od: std-proposals-request_at_[hidden]
> Komu: std-proposals_at_[hidden]
> Datum: 13. 7. 2021 19:01:01
> P?edm?t: Std-Proposals Digest, Vol 28, Issue 27
>
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> Today's Topics:
>
> 1. Re: A new proposal, new key-word definition for dynamic,
> run-time type-cast operations (Antoine Viallon)
> 2. Re: a new proposal. (Ga?per A?man)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 13 Jul 2021 15:01:31 +0200
> From: Antoine Viallon <antoine_at_[hidden]>
> To: std-proposals_at_[hidden]
> Subject: Re: [std-proposals] A new proposal, new key-word definition
> for dynamic, run-time type-cast operations
> Message-ID: <79FA6351-C0A4-4A70-9C28-73FD3C87341F_at_[hidden]>
> Content-Type: text/plain; charset="utf-8"
>
> Hello,
> I quickly read what you sent,
> And I have a question:
> Isn't there a "typeinfo" header containing something able to hold type
> information? There is typeindex also, if I'm not mistaken.
> Maybe the only thing you need is to be able to use such types in a
> dynamic_cast
>
> In any case, I see a very useful use-case for an argument parser for
> instance.
>
> Antoine Viallon
>
>
> -------- Courriel d?origine --------
> De?: Jaroslav Moravec via Std-Proposals <std-proposals_at_[hidden]>
> Envoy??: 13 juillet 2021 14:44:50 GMT+02:00
> ??: std-proposals_at_[hidden]
> Cc?: Jaroslav Moravec <j.moravec.email_at_[hidden]>
> Objet?: [std-proposals] A new proposal, new key-word definition for
> dynamic, run-time type-cast operations
>
>
> New proposal, version 2.
>
>
>
>
>
> Abstract
>
>
>
> The C++ language is here for more that 36 years and is still under
> development. Sometimes, C++ borrows some ideas from other programming
> languages, sometimes works on its own way. Presented proposal try to
> introduce a new type of basic variable which would be capable to hold a
> type
> of a variable or a type of a class or a struct. This variable should be
> capable to define target new type in type-cast operations such us: static_
> cast or dynamic_cast etc. Both at running time and at compilation time.
> Type
> of a variable or a class/struct is usually given by its unique name. Thus,
> the new basic variable should contain a string ? the name of basic
> datatype
> or a type of user defined datatype. This name is then used in the
> type-cast
> operation at running time. The target type is, of course, well known at
> compilation time.
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> Message: 2
> Date: Tue, 13 Jul 2021 17:42:32 +0100
> From: Ga?per A?man <gasper.azman_at_[hidden]>
> To: Std-Proposals <std-proposals_at_[hidden]>
> Subject: Re: [std-proposals] a new proposal.
> Message-ID:
> <CAANG=kUPxVURJhCJFqzYWRhsxDv6_Fz0rrbavj091d3OXvz71Q_at_[hidden]>
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>
> the dynamic_cast to a type-id is a really interesting call-site syntax for
> open multimethods - the problem isn't that this hasn't been tried (just
> look for multimethods) - the problem is we don't know of an efficient and
> correct way to implement the dispatch tables.
>
> If you are forced to write the switch statement based on the type-index
> yourself, then at least you need to list, exhaustively, the types you care
> about. Pattern matching is another way to do this. I'm not sure your
> proposal is implementable.
>
> G
>
> On Tue, Jul 13, 2021 at 11:26 AM Marcin Jaczewski via Std-Proposals <
> std-proposals_at_[hidden]> wrote:
>
> > I look like `dynamic` form C# but this mean it relay on reflection to
> > work correctly:
> > ```c#
> > dynamic d = x;
> > int i = d.item;
> > ```
> > is equal to
> > ```c#
> > DynamicType d = new DynamicType(x);
> > int i = (int)d["item"];
> > ```
> > C++ could have static reflection but this requires dynamic reflection
> > to work (static could generate dynamic but it will be costly).
> > Another thing is dynamic code generation other wise you can't have code
> > like:
> >
> > ```c++
> > std::cout << declarative_cast<type_var>(var);
> > ```
> > where type can be `int`, `long` or `std::vector<int>` and all need
> > have its own `<<` that is templated function that usually is inlined.
> > Does this mean `type_var` needs to store all possible template
> functions?
> >
> > Beside syntax like `declarative_cast<arg[0]->i>` is wrong as it mix
> > compile time template arguments with runtime arguments, something only
> > could work
> > if you use constexpr variables but it's not something your example wants
> > to do.
> >
> >
> > Lot better would expand `std::any` and allow easy way to have multiple
> > type callbacks like:
> > ```c++
> > std::any z = 17;
> >
> > vist_any<int, long, std::vector<int>>(z, [](auto& w) { std::cout <<
> > w; }); //you need name all types you want use
> > ```
> > and this is possible even if C++14
> >
> > wt., 13 lip 2021 o 11:27 Jaroslav Moravec via Std-Proposals
> > <std-proposals_at_[hidden]> napisa?(a):
> > >
> > > The proposal is in attachments. --
> > > Std-Proposals mailing list
> > > Std-Proposals_at_[hidden]
> > > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> > --
> > Std-Proposals mailing list
> > Std-Proposals_at_[hidden]
> > https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals
> >
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Received on 2021-07-14 00:55:54