220 28148 <6b360813-6dfd-484a-8258-3d3d1e41ca6e@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: edward.catmur@mavensecurities.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: capturing monads in lambda Date: Wed, 7 Sep 2016 15:00:27 -0700 (PDT) Lines: 169 Approved: news@gmane.org Message-ID: <6b360813-6dfd-484a-8258-3d3d1e41ca6e@isocpp.org> References: <5dba8d2b-6689-4781-a95a-c94896d98e55@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_232_87301542.1473285627597" X-Trace: blaine.gmane.org 1473285638 3699 195.159.176.226 (7 Sep 2016 22:00:38 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 7 Sep 2016 22:00:38 +0000 (UTC) Cc: szollosi.lorand@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDYODZPMTICBB7E3YK7AKGQEHII47JA@isocpp.org Thu Sep 08 00:00:34 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-qk0-f199.google.com ([209.85.220.199]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bhktT-0000DV-V8 for gclcip-std-proposals@m.gmane.org; Thu, 08 Sep 2016 00:00:32 +0200 Original-Received: by mail-qk0-f199.google.com with SMTP id w204sf53158576qka.3 for ; Wed, 07 Sep 2016 15:00:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=3Uni+SUxOsSfMlE5I5wNaTUuFqbJJmlxlZLj1AaCbcQ=; b=hDvDH0I87tE4t37VnfrLLhDfXj6Q71ZMyYUk1EAv1kNRAoKnmEaocdrmiYdu/WmjeF 4ZsDFBq5qXy/LSLzsO0Aj1Tqg1gN0PVpbwfPMjFO5LeG4VSVU9tAOoMDn1fam8RnLUH2 MVE8S0SCcga8vNoiRhrPags0sPa3Ucb18HTFLItobHfgVHKW5MyoDwNaWu7jWSlcVxGf wWhYj+veK7MmEXH1FDuQz3JWk/eeiwx+cbWoD2t+J4iezMTLP7rMDHhI4UI7Jhlk4oCn lfpldKlqlpA3UhxgVsFfKXNikpc0yOYm1jli5IDm9CAI7fUiBUSlTkTvZjSwia5+vo2P tULw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version:x-original-sender:reply-to :precedence:mailing-list:list-id:x-spam-checked-in-group:list-post :list-help:list-archive:list-subscribe:list-unsubscribe; bh=3Uni+SUxOsSfMlE5I5wNaTUuFqbJJmlxlZLj1AaCbcQ=; b=OZ8wmtjr1Y7xDBPwm9Z5fXtG2DuODjT18fKY0sskUftr3pB1RzRbsPS1to/URabQ0W r5rByArBBtRjqzvB0un1pEJgNgOx1YvB7vHI+36ceCRSDQlPAkfA7h5rET9tMBN9UAd8 cWv5HfVh20vA9VD0GNT+jbabVz1+3eLBlKU4kTeNzW3w3aN13kimt0wbFabmm8/Ox0xU nKRYl9CQe+L3Wcv69MM1wBzWEMibP/wBF4kkEe9E5dg9xmcVBA4SuKEWqXRlZAtgOMJT 0H1dvH7OtOD6EM7NFgsHODMeJWkRSr1mjXkin/yP96BQ8kU17OnGbiIsQlduVyMKPFeg vv0w== X-Gm-Message-State: AE9vXwNA91hm6Pjbd2YC/OQEmDhOGlnp/E+acqCVnpbZi+XbvRk3e1eAzlxGp7QlzkQw8Q== X-Received: by 10.159.38.133 with SMTP id 5mr41139353uay.9.1473285633075; Wed, 07 Sep 2016 15:00:33 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.36.214.81 with SMTP id o78ls1361243itg.22.gmail; Wed, 07 Sep 2016 15:00:28 -0700 (PDT) X-Received: by 10.36.39.214 with SMTP id g205mr238944ita.7.1473285628539; Wed, 07 Sep 2016 15:00:28 -0700 (PDT) In-Reply-To: <5dba8d2b-6689-4781-a95a-c94896d98e55@isocpp.org> X-Original-Sender: edward.catmur@mavensecurities.com 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:28148 Archived-At: ------=_Part_232_87301542.1473285627597 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wednesday, 7 September 2016 21:36:50 UTC+1, szollos...@gmail.com wrote: > > Hi, > > While thinking about for..else, I realized that it (and other language=20 > constructs) could be greatly simplified had we had the chance to capture= =20 > monads created by keywords like return, continue, break. Before proposing= =20 > any syntax/schematics, I'd first ask you, how would you feel about this= =20 > generally. The idea is something like: > [&return, break_=3D&break, break=3D...](){...} > > Capturing a monad assumes that it is valid to write it in the calling=20 > context. > > Note that capture is schematic, i.e., 'return' inside the lambda will=20 > destruct locals/parameters before performing caller's return; same holds= =20 > for break and continue. > I'm assuming that a lambda capturing a control flow keyword has to have=20 return type void. Still, what would this do? int f() { auto&& l =3D [&return](int i){ return i; }; (l(5), puts("hello"))= ; } --=20 This e-mail together with any attachments (the "Message") is confidential= =20 and may contain privileged information. If you are not the intended=20 recipient or if you have received this e-mail in error, please notify the= =20 sender immediately and permanently delete this Message from your system.=20 Do not copy, disclose or distribute the information contained in this=20 Message. =20 Maven Investment Partners Ltd (No. 07511928), Maven Derivatives Ltd (No.=20 07511840) , MVN Asset Management Limited (No. 09659116), Maven Europe Ltd= =20 (No. 08966593) & Maven Securities Holding Ltd (No. 07505438) are registered= =20 as companies in England and Wales and their registered address is Level 3,= =20 6 Bevis Marks, London EC3A 7BA, United Kingdom. The companies=E2=80=99 VAT = No. is=20 135539016. Only Maven Derivatives Ltd and MVN Asset Management Limited are= =20 authorised by the Financial Conduct Authority (Maven Derivatives Ltd FRN:= =20 607267, MVN Asset Management Limited FRN: 714429) --=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/6b360813-6dfd-484a-8258-3d3d1e41ca6e%40isocpp.or= g. ------=_Part_232_87301542.1473285627597 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Wednesday, 7 September 2016 21:36:50 UTC+1, szollos...@= gmail.com wrote:
Hi,

While thinking about for..else, I realized that it (and othe= r language constructs) could be greatly simplified had we had the chance to= capture monads created by keywords like return, continue, break. Before pr= oposing any syntax/schematics, I'd first ask you, how would you feel ab= out this generally. The idea is something like:
[&return, break_=3D&= amp;break, break=3D...](){...}

Capturing a monad assumes that it is = valid to write it in the calling context.

Note that capture is schem= atic, i.e., 'return' inside the lambda will destruct locals/paramet= ers before performing caller's return; same holds for break and continu= e.

I'm assuming that a lambda= capturing a control flow keyword has to have return type void.
<= br>
Still, what would this do?

=
int f()= { auto&& l =3D [&return](int i){ return i; };= (<= span style=3D"color: #000;" class=3D"styled-by-prettify">l(5), puts("hello")); }



This e-mail together with any attachments (the "Message"= ;) is confidential and may contain privileged information. If you are not t= he intended recipient or if you have received this e-mail in error, please = notify the sender immediately and permanently delete this Message from your= system. =C2=A0Do not copy, disclose or distribute the information containe= d in this Message.

=C2=A0

Maven Investment Partners Ltd (No. 07511928), Maven Derivatives Ltd (N= o. 07511840) , MVN Asset Management Limited (No. 09659116), Maven Europe Lt= d (No. 08966593) & Maven Securities Holding Ltd (No. 07505438) are regi= stered as companies in England and Wales and their registered address is Le= vel 3, 6 Bevis Marks, London EC3A 7BA, United Kingdom. The companies=E2=80= =99 VAT No. is 135539016. Only Maven Derivatives Ltd and MVN Asset Manageme= nt Limited are authorised by the Financial Conduct Authority (Maven Derivat= ives Ltd FRN: 607267, MVN Asset Management Limited FRN: 714429)

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