220 33718 <574320af-c1ae-4676-883c-ae4e91fcd874@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: gmisocpp@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: A more advanced switch Date: Wed, 9 Aug 2017 06:08:05 -0700 (PDT) Lines: 294 Approved: news@gmane.org Message-ID: <574320af-c1ae-4676-883c-ae4e91fcd874@isocpp.org> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_5174_1310644540.1502284085716" X-Trace: blaine.gmane.org 1502284087 8962 195.159.176.226 (9 Aug 2017 13:08:07 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 9 Aug 2017 13:08:07 +0000 (UTC) Cc: costelnistor12@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCM3TRNUXUDBBNUSVTGAKGQELSALQEY@isocpp.org Wed Aug 09 15:08:03 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-it0-f71.google.com ([209.85.214.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1dfQiP-00022K-Mn for gclcip-std-proposals@m.gmane.org; Wed, 09 Aug 2017 15:08:02 +0200 Original-Received: by mail-it0-f71.google.com with SMTP id o19sf52634349ito.5 for ; Wed, 09 Aug 2017 06:08:08 -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=bR8u9NOQoV+mq65EEVeSFrKVLGxDjXD4pi0GerPsTZ4=; b=PrXI8kIULEF52MryqhwooIiXb8HXCWCrJaM8Fkj0it1gIW2XjOe0Gj5/6Ol5JXUJ8g Zph0dOpFu6T9aSOcVG+Fz6iQK27tY0xTPf9y68ACWdY4jgw6u4mjHsLSsydJa/vS94Zv X++qEcjK8nsmuoEz3IR86cZjbVVAZ0U1TxFSfcwHpnk+OIwmsl4GGbDoE6cMjGmTo4Ao sGHVN2IgP2tZ22n1ik0EN9KTK31KYnGaNonIuiUGaRGeLDHL8wlOFicluLtbVJLvOaY4 xyhxv9qmGHKDKWdakTuloBeMRvxsDxmFf+aE5WZpwS4UB8zo7SieXQ6JSjBmR7nwWWMI XWUQ== 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=bR8u9NOQoV+mq65EEVeSFrKVLGxDjXD4pi0GerPsTZ4=; b=gbnVPo3i5VfUhu6wD4q0bpVDuAgLT9wu/BHsr6fzXSPNpFC1A823uG/c6/n7ODpIyk pYf1LXgXJ11Lb+1q46cCGQMCP6aBDGcxff27/qaZ5R90p92pINrc2wLhLuOvwxpHyACZ sfT0AOqRPFhijr3iAo66dSw4DXbyPzCKGhVhdhX1bE56q8JKnLMOgeirzO54w1kONxxs Np5/1tbTmsBMFZ43DI8HmA1xo3gQQs3YpJQPJrEwLV/4ZhCDVwTUPxCfG5GDLykw6ug9 506Z+Yc0lDZ7gQcDzlQ1MAQjxg4j9wUuT70hr7/pcYicTU5AhTONYcYz+speragDNtdl yrtg== 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=bR8u9NOQoV+mq65EEVeSFrKVLGxDjXD4pi0GerPsTZ4=; b=CvRkNsto+X2yu4IEirVr6QneovRk6oey9a2yxHMO+tOvUg757+jK5KeuB8w9YmBcTL pxK64AHdyCDpWmAub7fI9wwhTLcpn6GmWHdI2SEKBa0+X3Yz5pcpx1uII3h7LZA51wtQ 9MnL48Ne54eOrxBMx6U7JbXUe9F0/VK5ZvdGa8BLQBqkr7+BkOACkQyT7epftWP3GtGU z5arYdtSE53KuvOaL5G5m0syrvNGDvdSlbHZ0gRnLmIMC/vtn5nBNhNnhdRQttTADW2q kcWERbkjCmRfYfTj0yNIWmPqgsTCWDpOCik03M9t+hNg+dQWXZyHKIvRmP7nrNCQZ7Dl 8W6Q== X-Gm-Message-State: AIVw110jnEoXfFuV2/KxWOgBN2tqj5RlQK7Tozcypio79m8hujdmps4M 4UzDiw556+RYTLdT X-Received: by 10.36.41.7 with SMTP id p7mr5049739itp.25.1502284087731; Wed, 09 Aug 2017 06:08:07 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.173.71 with SMTP id w68ls4716011ioe.23.gmail; Wed, 09 Aug 2017 06:08:06 -0700 (PDT) X-Received: by 10.31.153.84 with SMTP id b81mr41624vke.14.1502284086377; Wed, 09 Aug 2017 06:08:06 -0700 (PDT) In-Reply-To: X-Original-Sender: gmisocpp@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:33718 Archived-At: ------=_Part_5174_1310644540.1502284085716 Content-Type: multipart/alternative; boundary="----=_Part_5175_654013518.1502284085717" ------=_Part_5175_654013518.1502284085717 Content-Type: text/plain; charset="UTF-8" I would very much like to see some changes to switch. I'd like something like: switch break (x) // cases break by default; { case 1: whatever(); case 2: whatever(); } I'd also like, for at least this variation of switch, for a case to be a scope by default, such that is ok: So that variables can be declared without requiring more braces. switch break (x) // cases break by default; { case 1: int z = 1; whatever(z); // not an error case 2: whatever(); } I think this would make most switch statements a lot less verbose. It seems a lot of the flexibility of the classic switch just isn't required. So this switch could be used when it's not and the existing switch can be used when it is. switch break seems easy to teach to me. So why not? On Wednesday, August 2, 2017 at 9:24:04 AM UTC+12, costeln...@gmail.com wrote: > Hello, I'm sorry if you talked about this here before, but I didn't watch > this group and I couldn't find this thing when searching. > > I'm coming from another language named Pawn, it looks like C ~80%, but it > has more advantages than C. Here's the official page: > https://www.compuphase.com/pawn/pawn.htm . > > A problem in C++: "switch" is exactly like in C, I think it deserves an > upgrade, as it can be used a lot, providing more speed and easier syntax > than lots of "if" ... "else if" ... "else" lines. I know that simply > updating it would break compatibility, so it may require another name > instead of switch, or you can find any other backwards compatible > alternative. I bet you can do this perfectly. > > For cases 0, 1, 2, 3, 4 and 5, 6 and "default" in C++ we have to do it like > switch( variable ) > { > case 0: case 1: case 2: case 3: case 4: > { > // ... > break; > } > > case 5: case 6: > { > // ... > break; > } > > default: > { > // ... > } > } > > We have to use "case" for every, well, case when specifying a sequence, > because it uses fallthrough. We have to use "break" to avoid that. I find > this bad. Because of the necessity of using "break" we can't just "break" > out of a loop if the switch is inside a loop. Also, if there are > consecutive cases we have to specify each one of them. Additionally, we > could also forget breaking. This "switch" isn't safe and is pretty old. > > In Pawn we can do it a lot better: > switch( variable ) > { > case 0 .. 4: > { > // ... > } > > case 5, 6: > { > // ... > } > > default: > { > // ... > } > } > > 1. There's no need for break, there's no fallthrough. Advantage: we can > easily "continue" and "break" loops from inside the "switch". > 2. We can use ".." if using several cases that are consecutive in the same > block of code, to specify an interval. > > I know that it's hard to have features accepted in such a popular > standard, but upgrading switch is something that should really be > considered ! C++17's [[fallthrough]] attribute is just as complicated as > the "switch". It needs to be added everywhere or else we would get warnings > (AFAIK). > > C++ needs a lot more syntactic sugar. Small and nice things are making the > language more likeable. I think that you should watch other languages too > for interesting small features. > -- 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/574320af-c1ae-4676-883c-ae4e91fcd874%40isocpp.org. ------=_Part_5175_654013518.1502284085717 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

I would very much like to see some cha= nges to switch.

I'd like something like:
=

switch break (x) // cases break by default;
{=
=C2=A0=C2=A0=C2=A0 case 1: whatever();
=C2=A0=C2=A0=C2= =A0=C2=A0case 2: whatever();
}

I'd also lik= e, for at least this variation of switch,=C2=A0for=C2=A0a case=C2=A0to be a= scope by default, such that is ok:
So that variables can be decl= ared without requiring more braces.

switch br= eak (x) // cases break by default;
{
=C2=A0=C2=A0=C2=A0= case 1: int z =3D 1; whatever(z); // not an error
=C2=A0=C2=A0= =C2=A0=C2=A0case 2: whatever();
}

I think this = would make most switch statements a lot less verbose.
It seems a = lot of the flexibility of the classic switch just isn't required.
=
So this switch could be used when it's not and the existing switch= can be used when it is.

switch break seems easy t= o teach to me. So why not?


On Wednesday, August 2, 2017 at 9:24:= 04 AM UTC+12, costeln...@gmail.com wrote:
Hello, I'm sorry if you talked about this here = before, but I didn't watch this group and I couldn't find this thin= g when searching.

I'm coming from another language n= amed Pawn, it looks like C ~80%, but it has more advantages than C. Here= 9;s the official page:=C2=A0https:/= /www.compuphase.com/pawn/pawn.htm .

A pro= blem in C++: "switch" is exactly like in C, I think it deserves a= n upgrade, as it can be used a lot, providing more speed and easier syntax = than lots of "if" ... "else if" ... "else" li= nes. I know that simply updating it would break compatibility, so it may re= quire another name instead of switch, or you can find any other backwards c= ompatible alternative. I bet you can do this perfectly.

= For cases 0, 1, 2, 3, 4 and 5, 6 and "default" in C++ we have to = do it like
switch( variable )
{
=C2=A0 =C2=A0 case 0: case : case 2: case 3: case 4:
=C2=A0 = =C2=A0 {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 // ...
=C2=A0 =C2=A0 =C2=A0 =C2=A0 break;
=C2=A0 =C2=A0 }

= =C2=A0 =C2=A0 case 5: ca= se 6:
=C2=A0 =C2=A0 {=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 // ...
=C2=A0 =C2=A0 =C2= =A0 =C2=A0 break;
=C2=A0 =C2=A0 }

=C2=A0 =C2=A0 default:
=C2=A0 =C2= =A0 {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 // ...=
=C2=A0 =C2=A0 }<= span style=3D"color: rgb(0, 0, 0);">
}

We have to use = "case" for every, well, case when specifying a sequence, because = it uses fallthrough. We have to use "break" to avoid that. I find= this bad. Because of the necessity of using "break" we can't= just "break" out of a loop if the switch is inside a loop. Also,= if there are consecutive cases we have to specify each one of them. Additi= onally, we could also forget breaking. This "switch" isn't sa= fe and is pretty old.

In Pawn we can do it a lot b= etter:
switch( variable )
{
=C2=A0 =C2=A0 case 0 .. 4:
=C2=A0 =C2=A0 {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 // ...
=C2=A0 =C2=A0 }

=C2=A0 =C2=A0= case 5,= 6:=
=C2=A0 =C2=A0 {=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 // ...
=C2=A0 =C2=A0 }

=C2=A0 =C2=A0 default:
=C2=A0 =C2=A0 {
=C2= =A0 =C2=A0 =C2=A0 =C2=A0 // .= ...
=C2=A0 =C2=A0 }
}

1. There's no need fo= r break, there's no fallthrough. Advantage: we can easily "continu= e" and "break" loops from inside the "switch".
2. We can use ".." if using several cases that are consecu= tive in the same block of code, to specify an interval.

I know that it's hard to have features accepted in such a popular= standard, but upgrading switch is something that should really be consider= ed ! C++17's [[fallthrough]] attribute is just as complicated as the &q= uot;switch". It needs to be added everywhere or else we would get warn= ings (AFAIK).

C++ needs a lot more syntactic sugar= .. Small and nice things are making the language more likeable. I think that= you should watch other languages too for interesting small features.
=

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/574320af-c1ae-4676-883c-ae4e91fcd874= %40isocpp.org.
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