220 7010 <525031B5.80202@wanadoo.fr> article Path: news.gmane.org!not-for-mail From: "Vicente J. Botet Escriba" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Unnamed LValues Date: Sat, 05 Oct 2013 17:35:17 +0200 Lines: 290 Approved: news@gmane.org Message-ID: <525031B5.80202@wanadoo.fr> References: <0d9b268f-cd3a-4048-a0a3-50cff02b28ce@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------060309030001090105030400" X-Trace: ger.gmane.org 1380987321 17284 80.91.229.3 (5 Oct 2013 15:35:21 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 5 Oct 2013 15:35:21 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDH67CONY4PBBN7DYCJAKGQEYJ6VU7Q@isocpp.org Sat Oct 05 17:35:24 2013 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lb0-f200.google.com ([209.85.217.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1VSTt3-0006qa-0C for gclcip-std-proposals@m.gmane.org; Sat, 05 Oct 2013 17:35:21 +0200 Original-Received: by mail-lb0-f200.google.com with SMTP id y6sf6653364lbh.11 for ; Sat, 05 Oct 2013 08:35:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:list-post:list-help :list-archive:list-subscribe:list-unsubscribe:content-type; bh=a5Mu87vdeYqvM13w6+XGXwDA5UQCgSd4/ipXxhHIa9w=; b=T422F4mR3vHe96yZoCellZD5vC+oQKQ16tYrEtAkDFjeEzw3cqy35GxBsK2xuEwLry iBAsGa4DPTiLfFh0qs0g/aW1e0DfvYmO/EqnG2X1fB0jwfo98yBpM1PvtQQcydty/rDS I2F6Ux/XdwCOPwBxTLQkgwoi4yiIdC92aMI96g1R5l+PAy4KVLUWD/B3+UQqLtF9Cx+F 0bpZBeBRGXdSOgUxhUsjFU2oAvj+jRtyM5prxdjkY64xm2u9KWZKRGHaHLMRVkl1GX8/ x2Af5Fl7o/ZBxCwAbha9subG+ms4K+PqABStDd/NxVW0gK5XyZnxs/8fepJisGCn6Ogk RrPA== X-Received: by 10.180.208.67 with SMTP id mc3mr5613496wic.1.1380987320204; Sat, 05 Oct 2013 08:35:20 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.107.41 with SMTP id gz9ls582788wib.33.gmail; Sat, 05 Oct 2013 08:35:19 -0700 (PDT) X-Received: by 10.15.94.201 with SMTP id bb49mr31999928eeb.23.1380987319078; Sat, 05 Oct 2013 08:35:19 -0700 (PDT) Original-Received: from smtp.smtpout.orange.fr (smtp08.smtpout.orange.fr. [80.12.242.130]) by mx.google.com with ESMTP id 7si15346091eeu.188.1969.12.31.16.00.00; Sat, 05 Oct 2013 08:35:19 -0700 (PDT) Received-SPF: neutral (google.com: 80.12.242.130 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) client-ip=80.12.242.130; Original-Received: from android-895509e2ec940b49.home ([92.139.19.223]) by mwinf5d16 with ME id ZTbH1m00J4omr7803TbJRz; Sat, 05 Oct 2013 17:35:18 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 In-Reply-To: <0d9b268f-cd3a-4048-a0a3-50cff02b28ce@isocpp.org> X-Original-Sender: vicente.botet@wanadoo.fr X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 80.12.242.130 is neither permitted nor denied by best guess record for domain of vicente.botet@wanadoo.fr) smtp.mail=vicente.botet@wanadoo.fr 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:7010 Archived-At: This is a multi-part message in MIME format. --------------060309030001090105030400 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Le 05/10/13 16:43, snk_kid a =E9crit : > A simpler solution would be to use plain higher-order functions,=20 > with-function patterns are very common in functional languages,=20 > something like: > > | > template > autowith_freeze(SomeWxWidgetClass*w,Function&&fn)->decltype(fn()) > { > WxScopeFreezescoped_freeze(w); > returnfn(); > } > | > > example usage: > > | > with_freeze(this,[&]()->void > { > with_freeze(other,[&]()->void > { > // do stuff. > }); > }); > | > > If you don't like the nesting you may be able to generalize this in=20 > various ways like using variadic templates so it may look more like this: > > | > |with_freeze(this, ||||other,||[&]()->void > { > // do stuff. > }); > | > | > > All this is useful, but this doesn't support control flow leaving the block= .. I proposed in [1] let-in statement and anonymous variable. With this=20 extension your PO could write it as WxScopeFreeze auto(this) *:* WxScopeFreeze auto(Other) *:* { } Whether ':' is appropriated to introduce the new variables could be=20 discussed. if the user has a Freeze function it could be even clearer auto=3DFreeze(this) : auto=3DFreeze(Other) : { } Best, Vicente [1] let-in statements and anonymous variables -=20 https://groups.google.com/a/isocpp.org/forum/#!topic/std-proposals/BfAtczj8= 1Kg --=20 ---=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. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --------------060309030001090105030400 Content-Type: text/html; charset=ISO-8859-1
Le 05/10/13 16:43, snk_kid a écrit :
A simpler solution would be to use plain higher-order functions, with-function patterns are very common in functional languages, something like:

template < typename Function >
auto with_freeze(SomeWxWidgetClass* w, Function&& fn) -> decltype(fn())
{
    WxScopeFreeze scoped_freeze(w);
    return fn();
}

example usage:

with_freeze(this, [&]() -> void
{
    with_freeze(other, [&]() -> void
    {
        // do stuff.
    });
});

If you don't like the nesting you may be able to generalize this in various ways like using variadic templates so it may look more like this:

with_freeze(this, other, [&]() -> void
{
   // do stuff.
});


All this is useful, but this doesn't support control flow leaving the block.

I proposed in [1] let-in statement and anonymous variable. With this extension your PO could write it as

WxScopeFreeze auto(this) : WxScopeFreeze auto(Other) : {
}

Whether ':' is appropriated to introduce the new variables could be discussed.

if the user has a Freeze function it could be even clearer

auto=Freeze(this) : auto=Freeze(Other) : {
}


Best,
Vicente

[1] let-in statements and anonymous variables - https://groups.google.com/a/isocpp.org/forum/#!topic/std-proposals/BfAtczj81Kg

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