Overloading

Posted Apr 26, 2014 17:54 UTC (Sat) by rsidd (subscriber, #2582)
In reply to: Overloading by apoelstra
Parent article: Porting the Go compiler to Go

I never learned C++ and I never learned Perl, basically because I couldn't read either -- both looked like line noise to me. My main exposure to C++ concepts, sad to say, is via this old fake Stroustrup interview, which has gems like this:

Take operator overloading. At the end of the project, almost every module has it, usually, because guys feel they really should do it, as it was in their training course. The same operator then means something totally different in every module. Try pulling that lot together, when you have a hundred or so modules.

(and much else, which is probably vvery familiar to LWN readers)

Overloading

Posted Apr 28, 2014 18:21 UTC (Mon) by drag (guest, #31333) [Link] (15 responses)

> I never learned Perl

You should. It's fun.

Overloading

Posted Apr 28, 2014 18:33 UTC (Mon) by HelloWorld (guest, #56129) [Link] (10 responses)

You should. It's fun.

If you're into BDSM I guess. This prints 11:

sub a {
  my $x = shift;
  sub b {
    $x;
  }
  \&b;
}
print a(1)->();
print a(2)->();

This prints 12:

sub a {
  my $x = shift;
  sub {
    $x;
  }
}
print a(1)->();
print a(2)->();

And this leaks memory every time it's called:

sub s {
  my $x;
  $x = \$x;
}

Thanks, but no thanks.

Overloading

Posted Apr 28, 2014 18:44 UTC (Mon) by rsidd (subscriber, #2582) [Link] (3 responses)

My boss 12 years ago wanted me to use perl, because it's what he used. I didn't know perl, I struggled to do a particular job for about 6 days, then (after listening to various other advice) said screw this, I'll try python (which also I didn't know). And I did it in 6 hours. Because I knew what I wanted to do, but couldn't figure out how to explain that to perl; with python it turned out to be straightforward.

As I remember, one stumbling block was this: the logical way to do what I wanted was via a list of lists, which in python would look like [[1,2],[3,4],[5,6]]. But perl flattens lists for you, and the syntax to get it to not flatten it was not widely known to people I talked to.

Overloading

Posted Apr 28, 2014 19:33 UTC (Mon) by madscientist (subscriber, #16861) [Link]

Feh. "The people you talked to" must have not known the first thing about Perl. Perl has its flaws (as does Python, Ruby, and just about everything else), but this is not one of them:

$ perl -e 'my @foo = ([0, 1], [3, 4]); print "$foo[0][1] $foo[1][0]\n";'
1 3

Overloading

Posted Apr 28, 2014 19:36 UTC (Mon) by dtlin (subscriber, #36537) [Link]

Lists (the non-reference kind) do get flattened in list context, but the exact same syntax - [[1,2],[3,4],[5,6]] - gives you a reference to an array of array references in Perl. Nobody you talked to had read perldoc perllol?

Overloading

Posted Apr 28, 2014 21:54 UTC (Mon) by drag (guest, #31333) [Link]

The shittiest thing about perl is that it's extremely difficult to google for.

Since perl has so much freedom each developer ends up their own idiosyncratic style. Since each style is so divergent it becomes very difficult to decypher what is going on. When you combine that with the fact that perl has so many little hidden variables and weird things that it does then it becomes difficult to understand what other people's code is doing.

I much rather prefer a language were there is just a small number of ways to do any single thing and one that enforces some sort of formatting rules and other things that helps make it more readable.

I am thinking that a lot of the overloading type things being discussed above for syntactic sugar type things may actually belong in the editor and not in the language. Like you can have all these language short cuts and 'jive terms' you prefer to use and have it expanded by the editor in the actual code you are working on so that it's easily read by other people that don't know your 'jive'. The editor can take care of translating back and forth for you, and if it can't figure it out then it's probably not worth doing.

Overloading

Posted Apr 28, 2014 21:32 UTC (Mon) by drag (guest, #31333) [Link] (5 responses)

> If you're into BDSM I guess. This prints 11:

If it hurts when you do that, don't do that.

Overloading

Posted Apr 28, 2014 22:33 UTC (Mon) by HelloWorld (guest, #56129) [Link] (4 responses)

The point is that Perl is incredibly inconsistent here: whether a closure is formed depends on whether a sub has a name or not. There is no justification for that kind of nonsense, and programming with a language that is so inconsistent is not what most people consider “fun”.

Overloading

Posted Apr 28, 2014 23:22 UTC (Mon) by alankila (guest, #47141) [Link]

The lords of Perl already knew about this class of mistake.

$ perl -we 'sub x { my $x = shift; sub y { $x } }'
Variable "$x" will not stay shared at -e line 1.

Perl's major fault is that too few of its warnings are fatal errors. I know, I know, you can opt-in to have warnings go fatal. My point is that the defaults are wrong.

Overloading

Posted Apr 28, 2014 23:45 UTC (Mon) by rgmoore (✭ supporter ✭, #75) [Link] (1 responses)

It's not that unreasonable. Perl makes a fairly big deal about anonymous values, and only anonymous functions can be turned into closures. If you like writing with closures, you'll learn the rules for them pretty quickly. This is the blessing and the curse of big languages like Perl. There's lots of cool features there to learn and use, but it means that different people program in different dialects that aren't as mutually comprehensible as you'd like. My take on this is that Larry Wall said he wanted Perl to be more like a human language than like a computer language, but that his idea of what human language is like is heavily influenced by being a native English speaker.

And I believe the properly snarky response to "If it hurts when you do that, don't do that." is "That's why I avoid Perl."

Overloading

Posted Apr 29, 2014 0:03 UTC (Tue) by HelloWorld (guest, #56129) [Link]

> It's not that unreasonable.
It is, it's completely nonsensical. I don't care about the excuses Larry might come up with.

Overloading

Posted Apr 29, 2014 6:21 UTC (Tue) by niner (subscriber, #26151) [Link]

Over here in the real world, most people of my team didn't know any Perl when they started to work for us. Nevertheless they all became productive by the end of their first week. And that's including learning about the framework, the ORM and our application. The language has never been a problem for them and they all like Perl very much nowadays.

Overloading

Posted May 2, 2014 12:29 UTC (Fri) by renox (guest, #23785) [Link] (3 responses)

> You should. It's fun.

I disagree with this: the more I develop in Perl, the less I like it..

Latest trap which caught me:
'do { ... } while(..)' doesn't work like 'while () { ... }', in the latter next/last work, not in the former???

Not fun!

Overloading

Posted May 2, 2014 17:51 UTC (Fri) by Wol (subscriber, #4433) [Link] (2 responses)

But that's common across MANY languages, not just perl. If you test the condition at the top of the loop, the loop doesn't always run. If you test at the bottom, you're guranteed at least one execution of the loop.

In fact, I think FORTRAN is illogical here. I can't remember much about it, but I used to program in FORTRAN IV and Fortran 77, and one of the switches available in Fortran was "always run loops at least once, like FORTRAN does". I can't remember whether that was the standard, or the Pr1me implementation, but I was well aware of it as something to be looked out for.

Cheers,
Wol

Overloading

Posted May 2, 2014 18:47 UTC (Fri) by dtlin (subscriber, #36537) [Link] (1 responses)

What renox means is the keywords last, next, and redo (analogous to break and continue in C) work inside while (..) { ... } but don't work inside do { ... } while (..). It's a syntactic oddity in Perl because do { ... } is an expression, not a block, and postfix while (..) turns an expression into a (looping) statement.

This is mentioned in perldoc perlsyn #Statement Modifiers, along with workarounds.

Overloading

Posted May 3, 2014 13:29 UTC (Sat) by madscientist (subscriber, #16861) [Link]

In my previous two jobs I wrote a lot of Perl, and I enjoyed using it. However, I hardly ever used do{}while() in my code, mainly due to these syntactical oddities. Every language has them, somewhere. It's easier to ignore them than to get burned by them.