Re: Re: Perl Style: About error messges opening files

[flyingmoose]

OT, but yet another style question for Abigail, since '=>' was like crazy again...

I've noticed you use => in place of commas .. a lot. <seinfeld>not that there is anything wrong with that</seinfeld>. I'm still one that uses => only for hash construction, when I need to imply a key-value pair, or maybe in a map, but anyway, when I need the implicit LHS quoting and a comma.

In one of your examples, you gave something like

system mkdir => -p => $foo;

while most would do something closer to:

system("mkdir -p $foo");

Care to explain why this is syllistically more interesting to you? My guess is no, but we're on a style thread and this just looks odd to me. I'm thinking you were nearly eaten by a pack of rabid commas when you were a child or something :) Ok, so I'm not going to use '=>' any more because of what you might say, I'm just curious ... sort of like a 'where did that accent come from' type of question.

(commence with the moose stoning)

[Abigail-II]

The difference between system("mkdir -p $foo") and system mkdir => -p => $foo; is more than just the style of commas. Single argument system is subject to shell interpretation, while multi argument system is not.

Having said that, I tend to use => to separate arguments which have totally different roles - most often to separate the first argument from the rest:

    push @array => 1, 2, 3, 4;
    printf "%s %6d %s" => $foo, $bar, $baz;
    pack "C" => $var;
    splice @array => 0, 3 => "foo", "bar", "baz";

Etc. I've used that long before people started preaching that => was some kind of pair creator. It never was, and still isn't. And I'm not the only one using this style, Larry Rosler (of GRT fame) was a vivid user of this style as well.

Abigail

[flyingmoose]

A'ight, thanks! ... that explains a lot!

[adrianh]

I would imagine that Abigail avoided:

system("mkdir -p $foo");

because that would be interpreted by the shell, and would foul up if (for example) $foo contained a filename with spaces. The advantage of using the arrow instead of the comma is that you can get away with less quoting, compare:

system mkdir => -p => $foo;
system 'mkdir', '-p', $foo;

Same number of chars, arguably more readable.

[eserte]

To safe another char, one could write

system qw(mkdir -p), $foo;

But best would be if perl had a backtick operator like lisp (that is elisp, don't know about other lisp implementations):

system `(mkdir -p ,$foo);

[eserte]

You surely mean the list variant of system: system "mkdir", "-p", $foo

[flyingmoose]

Eh. $foo did not come from untrusted user input in my example.

Fair point, but it depends on what domain you work in. In fact, none of my programs take any user input :)

[eserte]

It hasn't to be user input. It could be the result of a File::Find::find run in a directory where some malicious Windows user created a directory name with whitespace in it.