Re: cleaning perl code

On 4/11/20 12:28 PM, Mark Dilger wrote:
>
>> On Apr 11, 2020, at 9:13 AM, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)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
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