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Groups > comp.lang.c++ > #69894
| From | "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Substitution failure can be an error |
| Date | 2019-11-18 18:49 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <qqulj5$jd1$1@dont-email.me> (permalink) |
As the title says, substitution failure can be an error:
#include <iostream>
#include <initializer_list>
#include <type_traits>
using namespace std;
template< class Value >
auto is_in( const initializer_list<Value>& list, const Value v )
-> bool
{ return false; }
//-----------------------------------
template< class Int >
struct S
{
using U = make_unsigned_t<Int>;
U m;
S( Int x, Int ): m( U( x ) ) {}
};
template< class Int >
auto is_in( const S<Int>& s, const Int v )
-> bool
{ return true; }
auto main()
-> int
{ return 100 + is_in( {&cout, &cerr}, &clog ); }
For now I've just used a `std::enable_if` to restrict `S` to integral
types, but I don't feel that this can be the best solution.
Like, it feels like a kludge, somewhat dirty.
- Alf
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Substitution failure can be an error "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-18 18:49 +0100
Re: Substitution failure can be an error Vir Campestris <vir.campestris@invalid.invalid> - 2019-11-18 21:54 +0000
Re: Substitution failure can be an error Sam <sam@email-scan.com> - 2019-11-18 18:12 -0500
Re: Substitution failure can be an error Melzzzzz <Melzzzzz@zzzzz.com> - 2019-11-19 03:53 +0000
Re: Substitution failure can be an error "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-19 12:48 +0100
Re: Substitution failure can be an error Melzzzzz <Melzzzzz@zzzzz.com> - 2019-11-19 19:48 +0000
Re: Substitution failure can be an error "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-19 21:31 +0100
Re: Substitution failure can be an error Melzzzzz <Melzzzzz@zzzzz.com> - 2019-11-19 21:20 +0000
Re: Substitution failure can be an error "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-19 22:51 +0100
Re: Substitution failure can be an error Melzzzzz <Melzzzzz@zzzzz.com> - 2019-11-19 21:58 +0000
Re: Substitution failure can be an error David Brown <david.brown@hesbynett.no> - 2019-11-20 09:19 +0100
Re: Substitution failure can be an error Öö Tiib <ootiib@hot.ee> - 2019-11-20 02:16 -0800
Re: Substitution failure can be an error scott@slp53.sl.home (Scott Lurndal) - 2019-11-20 14:13 +0000
Re: Substitution failure can be an error Öö Tiib <ootiib@hot.ee> - 2019-11-20 08:34 -0800
Re: Substitution failure can be an error David Brown <david.brown@hesbynett.no> - 2019-11-21 12:34 +0100
Re: Substitution failure can be an error Öö Tiib <ootiib@hot.ee> - 2019-11-21 05:29 -0800
Re: Substitution failure can be an error David Brown <david.brown@hesbynett.no> - 2019-11-21 15:58 +0100
Re: Substitution failure can be an error Christian Gollwitzer <auriocus@gmx.de> - 2019-11-20 11:12 +0100
Re: Substitution failure can be an error Öö Tiib <ootiib@hot.ee> - 2019-11-20 04:25 -0800
Re: Substitution failure can be an error Öö Tiib <ootiib@hot.ee> - 2019-11-20 06:05 -0800
Almost Always Auto? (was Re: Substitution failure can be an error) Vir Campestris <vir.campestris@invalid.invalid> - 2019-11-22 21:46 +0000
Re: Almost Always Auto? (was Re: Substitution failure can be an error) Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-11-23 09:29 +0000
Re: Almost Always Auto? (was Re: Substitution failure can be an boltar@nowhere.co.uk - 2019-11-23 17:23 +0000
Re: Almost Always Auto? (was Re: Substitution failure can be an error) Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-11-28 12:46 -0800
Re: Almost Always Auto? (was Re: Substitution failure can be an error) "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-24 00:26 +0100
Re: Almost Always Auto? (was Re: Substitution failure can be an error) "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-24 00:28 +0100
Re: Almost Always Auto? (was Re: Substitution failure can be an error) "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-24 00:45 +0100
Re: Almost Always Auto? (was Re: Substitution failure can be an boltar@nowhere.co.uk - 2019-11-24 10:47 +0000
Re: Almost Always Auto? (was Re: Substitution failure can be an Melzzzzz <Melzzzzz@zzzzz.com> - 2019-11-24 13:37 +0000
Re: Almost Always Auto? (was Re: Substitution failure can be an boltar@nowhere.co.uk - 2019-11-25 11:08 +0000
Re: Substitution failure can be an error Manfred <noname@add.invalid> - 2019-11-20 18:46 +0100
Re: Substitution failure can be an error "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-11-21 06:02 +0100
Re: Substitution failure can be an error Manfred <noname@add.invalid> - 2019-11-21 15:50 +0100
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