220 33755 article Path: news.gmane.org!.POSTED!not-for-mail From: Cleiton Santoia Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: A more advanced switch Date: Wed, 9 Aug 2017 16:29:11 -0700 (PDT) Lines: 351 Approved: news@gmane.org Message-ID: References: <5a36b655-b2a9-4be2-8599-465810cfd1b3@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_290_1863104350.1502321351131" X-Trace: blaine.gmane.org 1502321355 27557 195.159.176.226 (9 Aug 2017 23:29:15 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 9 Aug 2017 23:29:15 +0000 (UTC) Cc: costelnistor12@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCBMVWMTUUNBBR5VV3GAKGQE2OBWTLI@isocpp.org Thu Aug 10 01:29:10 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f72.google.com ([209.85.214.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dfaPS-0006gL-Q8 for gclcip-std-proposals@m.gmane.org; Thu, 10 Aug 2017 01:29:07 +0200 Original-Received: by mail-it0-f72.google.com with SMTP id 77sf8971586itj.4 for ; Wed, 09 Aug 2017 16:29:13 -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:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=dN8jpmo4Mua8Reob+cRuhpIhPekDuvyDKl+Yk6W4z1M=; b=JbDUKy7LdaICixVEgRTVeqQwfd2QYQu/legIE/nynQr5uvlPmVwcsaB6/Pwh78PRID p67Xn2ScuACFJeFn+jHHBV4cTHe5Pr4QSP3EIlOB/WdZHuIn5QMnphvnzW+UG9YitBLW qpfW2mjZLEloyHzkWUfvmM4AhLeugDutad2nk8lxLXAeebX5ySL18djZ51MLTub+mNem E/SGC+PPYGcZh2ntxaRgGRaUB3nBbp0pugR6cFYuZ/iFMnN5+ZYN3MYJe7YNCPwKvIAw upkeGYLXEOONEPuk/Eo3H/FMS6DV9VQHWMr8PGxHr+H7XCUnNsCDOF/ITq7uED0dxezx gxPg== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=dN8jpmo4Mua8Reob+cRuhpIhPekDuvyDKl+Yk6W4z1M=; b=eURpT9lLPsT01PHQLrDgrUbf/0wii9GRxgJiJDQiSteVHiR6qiV1W58d9lwpDW7Qr3 t6dkYIHPcKvEtp5CzeN88OWahprN220RwOM7ExanUPnwYFLGy/bYo2KJjEg4Tqb53R3L 3JTAApC6cyyBmQjvkUy87svq7bPZLVgLd5VRYfh1YSVlklemzdbyXJdfbT2tYG9a1xm/ /EhuPqb7jrmnd9yhPb+UEEGsob89I4G80WKrpT43wNFr+FD1StcDzgf/48Dl2WaeeyTt 6mizhA3ZnffElfJ204ckOJulJNu9RZoZroQ3dK5b+50+VfK0P+nyK3+mRBe6j1tr/cVP 8ckg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; 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=dN8jpmo4Mua8Reob+cRuhpIhPekDuvyDKl+Yk6W4z1M=; b=kOqAI2Qy9Pdkfq72t+Cz8XSrvKqKxepC0a/w4Wjpa7xsO3UJlwfThrAgJ0SADuBTyf i4Rgpi9Y+YNcqQxy5/mJyFJNEsw5u0Qsk8lCSlyrJ6dZ3O1UnrpyKRNVxDRkv3/RvUpA E2CDRbNQeKdB57ONBEuKlkitSZmFSCnS++IU1m+F9I+SpBSmbDpHXz3U2LJLe4un4HW1 5ddFdbDQsp34TTcC9PxnCAQST9j3YPIp7Wx6i/x+8JRhPj3IT6Oa2jo88sJjZgTDNHYl p18r5Jkf4CyvAfziqGqfeKLnLlwv+Po3kv4zjBI+0Zb/PO//a8HwYfinH85ejl9kSbye k/vw== X-Gm-Message-State: AHYfb5h74al0pkEKkkGf0ihSU7riQsV3HYkxdP73FZWWSGuOjUNn9gao 4WRa+IGrgCOyyVD/ X-Received: by 10.107.46.29 with SMTP id i29mr6180413ioo.55.1502321352792; Wed, 09 Aug 2017 16:29:12 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.178.88 with SMTP id b85ls11549496iof.5.gmail; Wed, 09 Aug 2017 16:29:11 -0700 (PDT) X-Received: by 10.31.157.209 with SMTP id g200mr52634vke.9.1502321351611; Wed, 09 Aug 2017 16:29:11 -0700 (PDT) In-Reply-To: X-Original-Sender: cleitonsantoia@gmail.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:33755 Archived-At: ------=_Part_290_1863104350.1502321351131 Content-Type: multipart/alternative; boundary="----=_Part_291_1921638203.1502321351132" ------=_Part_291_1921638203.1502321351132 Content-Type: text/plain; charset="UTF-8" > That's not a switch, that's an if-else chain masquerading as a switch. > I would strongly > suggest adding a pattern-matching mechanism and leaving switch alone; > switch has > semantics that don't fit into general matching, and other expectations > that a general > matching mechanism doesn't have, including recommendations against using > switch > because switch does fall-through and a general matching mechanism > probably shouldn't. > This is good... I want a *gmm* (general matching mechanism) and I think that the keyword for it should be *switch*. Said that, now we need to a way to tell the compiler that we are talking about the "new" switch, maybe via positional token ( megazord ), analogous to "switch break" already mentioned. This switch will apply to more than one expression at a time, and use "==" for each element and "default break" unless you specify via [[fallthrough]] std::string x = "AF-56"; enum YesNo{ NO,YES } answer = YesNo.YES; switch megazord ( answer; int k = 90; x.substr(0,2) ) { case NO; default : // enters here if answer is NO and not check any of the others // Code case YES; 10r.100r; "[_a-zA-Z][_a-zA-Z0-9]{0,30}"regex : // ranges and regular expressions, nice ! // Code case YES; 10r.100r; "AA"r."AX"r : // ranges can be of std::strings too ( or const char* ), why not ? // Code case default: } I think this covers almost all problems: 1 - Can be used with std::string ( or anything else: std::variant, std::string_view, std::vector ) 2 - Can be used with ranges ( analogous to ".." operator ). I wonder... can I use two unary postfix "dot" operator in a sequence ? 3 - Can be used with many arguments at once. 4 - Execute functions, make temporaries and declare variables at the beginning 5 - Avoid unintentional fallthrough 6 - Leave the old switch alone But still get the problem : switch megazord ("A") { // this is a const char * pointer and one cannot overload ''==" } We need switch megazord("A"s) { // <- string literal } P.S. I know... I know... megazord is not a good name, may be 'batman' instead -- 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 email 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/cb29f028-f791-4cb7-8593-5683995839f3%40isocpp.org. ------=_Part_291_1921638203.1502321351132 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

That'= s not a switch, that's an if-else chain masquerading as a switch.
I would strongly
suggest adding a pattern-matching mechanism and leaving switch alone; s= witch has
semantics that don't fit into general matching, and other expectati= ons
that a general
matching mechanism doesn't have, including recommendations against = using switch
because switch does fall-through and a general matching mechanism
probably shouldn't.

This is good...
I want a *gm= m* (general matching mechanism) and I think that the keyword for it should = be switch.

Said that, now we need to a way = to tell the compiler that we are talking about the "new" switch, = maybe via positional token ( megazord ), analogous to "switch break&qu= ot; already mentioned.=C2=A0

This switch will appl= y to more than one expression at a time, and use "=3D=3D" for eac= h element and "default break" unless you specify via [[fallthroug= h]]


st= d::string x =3D "AF-56";<= /span>
enum YesNo{ NO<= /span>,YES= } = answer =3D= =C2=A0YesNo.YES;

sw= itch=C2=A0megazord=C2=A0( answer;=C2=A0int k =3D 90;=C2=A0x.substr(<= /span>0,2) ) {
case NO;=C2=A0default <= span style=3D"color: rgb(102, 102, 0);">: <= span style=3D"color: rgb(136, 0, 0);">// enters here if answer is NO and not check any of th= e others
=C2=A0 =C2=A0 // Code<= br>case YES;=C2=A010r.100= r;=C2=A0"[_a-zA-Z][_a-zA-Z0-9]{0,30}&quo= t;regex=C2=A0<= /span>: // ranges and regular expressions, nice !<= br>=C2=A0= =C2=A0=C2=A0// Code
case=C2=A0YES;=C2=A010r.100r;=C2=A0<= /span>"AA"r."AX"<= /span>r=C2=A0:=C2=A0// ranges ca= n be of std::strings too ( or const char* ),=C2=A0why not ?
=C2=A0 =C2=A0=C2=A0// Code
c= ase d= efault:
}

I think this covers almost all problems:
1 - Can= be used with std::string ( or anything else: std::variant, std::string_vie= w, std::vector =C2=A0)=C2=A0
2 - Can be used with ranges ( analog= ous to ".." operator ). I wonder... can I use two unary postfix &= quot;dot" operator in a sequence ?
3 - Can be used with many= arguments at once.
4 - Execute functions, make temporaries and d= eclare variables at the beginning
5 - Avoid unintentional fallthr= ough
6 - Leave the old switch alone

But = still get the problem :=C2=A0

switch megazord (&qu= ot;A") { // this is a const char * pointer and one cannot overload = 9;'=3D=3D"
}

We need
=
switch megazord("A"s) { =C2=A0// <- string lite= ral=C2=A0
}



P.S. = I know... I know... megazord is not a good name, may be 'batman' in= stead

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