220 32532 <9064929.QEV8q21eIZ@tjmaciei-mobl1> article Path: news.gmane.org!.POSTED!not-for-mail From: Thiago Macieira Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: relaxing rules for ternary operator. Allow incompatible types. 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[2a01:4f8:d13:f81:21c:14ff:fe01:12a3]) by mx.google.com with ESMTP id c16si4371353ywb.155.2017.05.20.12.29.54 for ; Sat, 20 May 2017 12:29:54 -0700 (PDT) Received-SPF: pass (google.com: domain of thiago@macieira.org designates 2a01:4f8:d13:f81:21c:14ff:fe01:12a3 as permitted sender) client-ip=2a01:4f8:d13:f81:21c:14ff:fe01:12a3; Original-Received: from tjmaciei-mobl1.localnet (unknown [IPv6:2601:1c0:4501:5f9f:6da5:acd8:4cde:e926]) by gondolin.macieira.info (Postfix) with ESMTPSA id 4D9BB12C001 for ; Sat, 20 May 2017 12:29:53 -0700 (PDT) In-Reply-To: <1b5ee8eb-53df-4e98-af2f-829c7bc2e5b2@isocpp.org> X-Original-Sender: thiago@macieira.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of thiago@macieira.org designates 2a01:4f8:d13:f81:21c:14ff:fe01:12a3 as permitted sender) smtp.mailfrom=thiago@macieira.org Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:32532 Archived-At: On s=C3=A1bado, 20 de maio de 2017 10:41:56 PDT ma.kalbfuss@web.de wrote: > Hi Guys, >=20 > I had the following situation: >=20 > I have a Group of StaticSet classes with a compatible interface but > distinct in there concrete type. empty_set is not an intervall! > I tried the following: >=20 >=20 > auto dec_digit =3D make_interval('0', '0' + std::min(base, DECIMAL_BASE) = - 1); > auto upper_digit =3D (base > DECIMAL_DIGIT) ? make_interval('A', 'A' + (b= ase > - 1 - DECIMAL_BASE)) : empty_set; > auto lower_digit =3D (base > DECIMAL_DIGIT) ? make_interval('a', 'a' + (b= ase > - 1 - DECIMAL_BASE)) : empty_set; >=20 >=20 > Wouldn't it be possible to allow such code, especially in conjunction wit= h > concepts? No. lower_digit must have exactly one type, determined at compile-time. Wha= t=20 you're asking for would cause the type to be determined at runtime, which i= s=20 not possible in C++. Alternatives: * convert empty_set to make_interval's type * convert either to a common type (which you need to be explicit about, so = it=20 won't work with auto) * use std::variant --=20 Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org Software Architect - Intel Open Source Technology Center --=20 You received this message because you are subscribed to the Google Groups "= ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/9064929.QEV8q21eIZ%40tjmaciei-mobl1. .