From: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
To: Mark Dilger <mark.dilger@enterprisedb.com>
Cc: Noah Misch <noah@leadboat.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: cleaning perl code
Date: Sat, 11 Apr 2020 12:47:55 -0400
Message-ID: <5b2ae2b0-8b09-d153-275a-24e7b2ac7989@2ndQuadrant.com> (raw)
In-Reply-To: <97813D8D-F185-4998-8CF8-5678746E7DEE@enterprisedb.com>
References: <e56f6fb6-38d5-8450-577c-24eb5d63f2e1@2ndQuadrant.com>
<20200411043014.GA590991@rfd.leadboat.com>
<0a4406d5-b428-4831-8ed9-c36764360f57@2ndQuadrant.com>
<97813D8D-F185-4998-8CF8-5678746E7DEE@enterprisedb.com>
On 4/11/20 12:28 PM, Mark Dilger wrote:
>
>> On Apr 11, 2020, at 9:13 AM, Andrew Dunstan <andrew.dunstan@2ndquadrant.com> wrote:
> Hi Andrew. I appreciate your interest and efforts here. I hope you don't mind a few questions/observations about this effort:
Not at all.
>
>> The
>> last one fixes the mixture of high and low precedence boolean operators,
> I did not spot examples of this in your diffs, but I assume you mean to prohibit conditionals like:
>
> if ($a || $b and $c || $d)
>
> As I understand it, perl introduced low precedence operators precisely to allow this. Why disallow it?
The docs say:
Conway advises against combining the low-precedence booleans ( |and
or not| ) with the high-precedence boolean operators ( |&& || !| )
in the same expression. Unless you fully understand the differences
between the high and low-precedence operators, it is easy to
misinterpret expressions that use both. And even if you do
understand them, it is not always clear if the author actually
intended it.
|next| |if| |not ||$foo| ||| ||$bar||; ||#not ok|
|next| |if| |!||$foo| ||| ||$bar||; ||#ok|
|next| |if| |!( ||$foo| ||| ||$bar| |); ||#ok|
I don't feel terribly strongly about it, but personally I just about
never use the low precendence operators, and mostly prefer to resolve
precedence issue with parentheses.
>
>> and the use of commas to separate statements
> I don't understand the prejudice against commas used this way. What is wrong with:
>
> $i++, $j++ if defined $k;
>
> rather than:
>
> if (defined $k)
> {
> $i++;
> $j++;
> }
>
I don't think the example is terribly clear. I have to look at it and
think "Does it do $i++ if $k isn't defined?"
In the cases we actually have there isn't even any shorthand advantage
like this. There are only a couple of cases.
cheers
andrew
--
Andrew Dunstan https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: andrew.dunstan@2ndquadrant.com, mark.dilger@enterprisedb.com, noah@leadboat.com
Subject: Re: cleaning perl code
In-Reply-To: <5b2ae2b0-8b09-d153-275a-24e7b2ac7989@2ndQuadrant.com>
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