From: Andrew Dunstan <andrew.dunstan@2ndquadrant.com>
Subject: Re: cleaning perl code
To: Mark Dilger <mark.dilger@enterprisedb.com>
Cc: Noah Misch <noah@leadboat.com>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
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>
Autocrypt: addr=andrew.dunstan@2ndQuadrant.com; prefer-encrypt=mutual;
 keydata=
 mQENBE7KWFkBCAClridxur2AIc7eW2AR7izbfp3EnNefie2HbLF0izW5Ik5UjX2HBXBx4syI
 gY6b0ugohXrr274+baoAlvSbq6cAoQuEVrk5IZFzt20b1Xkx65FwGSEj526yiKLocqkJceSq
 Xr9xcA5SGY+FZv441chh5SU92v4q6z+6LPpoHOh97ptAVXZYNTtU0LevyvD5lja0TzbvJm6C
 eFXitJfnm1pLEr0DGJCR/iUOl/N62Kh4855zZC7NHIjQHPOvV5Stz/l5ilDhvGVk+xkXFPys
 SjZoUr1rXhYLpiyi5sR0X9FHXT0KnGuz1F5ERO7ZTLSSQ6fJwPj6gOk9K+vvoKvoeql5ABEB
 AAG0L0FuZHJldyBEdW5zdGFuIDxhbmRyZXcuZHVuc3RhbkAybmRRdWFkcmFudC5jb20+iQFY
 BBMBAgBCAhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgBYhBOQ+WEYd/Hy/RGkVpZn6f8tZ
 /DuBAhkBBQJd1pSYBQkSzqMsAAoJEJn6f8tZ/DuBJmEIAIVFBIC3qGqh+YTPVTkfowwxpHz0
 tZSPjZ6GS/5y62kgoZrZOVXw+Rg2ceuMM3a+In/RRjTx4bembgYqRKgzXlDfiNBJeq5ioVuN
 H1faDKE2lm5a6QkRQ2JU6DKf60fqSJGP5LisCUr1V0wz6EnlO31ArrKtXCNB+yk0KDAS6o6I
 Ql4pkXpr+vq4iilwJmiJOqTBam0LmQE7ulYCCYU8Z6MkpiSl+dO7QSramcGyxauQRI3a7gcq
 dpo8Vrv3gFTQDeMYxk7cqZp08pIVH5XR0+LgBz4X84f59rA/VAKlC/r6CyEQk59rvDLxCMyP
 2buoj51Z25N3MVghRDGcsU6mT7e5AQ0ETspYWQEIANGc4zQULOxhbqO2dyD51YhqCNRmm9oK
 Waqf+wmW4tpDe/VVcxAnNizd4LWCHfzpb5cHAtGkOPePMfzWVf6nvdF7d3eglbtf59+zG7O7
 llV0xSSoFiieQBsrGvqDInXYX/4mRRXMtyhM353/tixC9RWLs1oofyYmCPPXXY7h9R7en3B8
 BoVrRFcdzlIY/NFNhFGW/9dkEiGjgna2Rk6e15kln4ZvFBWUg23p93w/pqXcxY6+k/8TEk+C
 4R+M6w7o2PLGOjdZ+kPiUcw5H85zf/yZJwQXzisXaNduwWB6Vads9YC9dj6kPR1c4VGRqAaY
 L++LAEOqrlvm2TvqQqZRtnEAEQEAAYkBJQQYAQIADwIbDAUCXdaUtAUJEs6jVQAKCRCZ+n/L
 Wfw7gQi5B/9sHbmRloZNCWWwZGm+O9iG/JGQxS0WWa4GaZqzqSTWOft2/gO0Bgag89r1djq4
 PFgSZtzHvKQpqYz/7HkPrWh1jpcS83i/uYY1uyHXUUtpdEmn4buNObEtD0YNaJkGdhASsECq
 6akw+u7WJYmAHs/SpR6ok6HqLw7JHDVc2h5dViLfTk0qrgDa7sq/LVMoJje5Ct/Ku3YaWAV6
 YSmzoPP5BmPVFqP11OMQkCqurIu9vTLXKFWX623vCmqRDHJ6e5GCDHbH8USU+4wJBfPymZkd
 cA7NGm/mmWeJiWBFIDyjzYxrjku8ty9TZJVsaRXnS+OFQzXz9Eu2wTpKdHij46uY
Message-ID: <5b2ae2b0-8b09-d153-275a-24e7b2ac7989@2ndQuadrant.com>
Date: Sat, 11 Apr 2020 12:47:55 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.6.0
MIME-Version: 1.0
In-Reply-To: <97813D8D-F185-4998-8CF8-5678746E7DEE@enterprisedb.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: bulk


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