The taming of the newbie - a comedy on IRC

http://use.perl.org/~masak/journal/40110

by draegtun • 17 years ago

25 25 17 years ago

use.perl.org

RyanMcGreal2• 17 years ago

> nowadays we have flip for strings, reverse for lists, and invert for hashes

That seems utterly insane.

gcb• 17 years ago

it's just for the benefits of that code poetry thing.

the sole reason perl is used.

perlgeek2• 17 years ago

It follows Perl's philosophy very closely.

As an example: in Javascript, the binary + operator means either addtion or concatenation, depending on the type of the left-hand side. In Perl there are different operators for that, + for addition and . for concatenation.

That means that you have more operators, but you need less type conversions, because they happen implicitly.

This now follows the same philosophy: different operations have different names. List reversal is not the same as string reversal. Neither is hash inversion.

Within this context it's the most logical thing you can do.

tptacek5• 17 years ago

Wait, nothing you just said makes renaming "reverse" "flip" more logical.

masak8• 17 years ago

If I may try to briefly explain/defend the naming as well as expand on the need for it...

In Perl 5, 'reverse' did all of the three things: it reversed strings (in scalar context), or lists/hashes (in list context). The latter two weren't really distinguished, since a hash in Perl 5 is just an (even-element) list that you assign to a hash variable.

In Perl 6, 'wantarray' http://perldoc.perl.org/functions/wantarray.html is gone, and not even built-in methods rely on figuring out the void/scalar/list context of the caller. Which means that we don't do the trick described in the blog post to make 'reverse' do either string or list reversal.

Very well, no problem. What we lack in 'wantarray' we make up with a type system. We just stick the string-reversing 'reverse' method on the type Str, and the list-reversing one on the type List. All good and well. (In fact, we put the string-reversing one on Any, and let it coerce to Str when needed.)

But wait. There are some corner cases where this causes problems. Sometimes a scalar variable contains a list of things, and sometimes a list contains but one element. In either case, we try to magically guess between the two uses, and get it wrong. So maybe making those two behaviours homonyms wasn't too good an idea after all.

Hence the need for distinguishing 'flip' and 'reverse'. By distinguishing 'invert', we can make it a bit smarter in case of hash key collisions. The 'magical guessing' dilemma goes away, because it's clear you mean a list when you say 'reverse' and a string when you say 'flip'.

The names are fairly well-chosen, considering what they do. You flip a single thing (string), reverse the order of a sequence of elements (list), and invert a mathematical mapping (hash).

RyanMcGreal2• 17 years ago

Thanks for the explanation. I guess I'm in the habit of thinking of a string as a list of characters. :)

tptacek5• 17 years ago

This sentence is even worse:

"Instead, reverse responds to its surroundings and figure out what they expect. $string = reverse $string is a scalar assignment, and expects a scalar. print reverse $string, as integral explains, puts reverse in list context, so it reverses the list of one thing ($string), i.e. doing nothing."

At least "flip" is just a very dumb name.

masak8• 17 years ago

> At least "flip" is just a very dumb name.

It's funny. I just registered on HN, and on my way in I took the time to read http://ycombinator.com/newswelcome.html where the expectations on comments are outlined:

"What we especially discourage are comments that are empty and negative—comments that are mere name-calling."

Do you wish to make your negative comment about 'flip' less empty? Or have you expended your fount of criticism already?

10ren2• 17 years ago

In C, parentheses mean expression grouping, function invocation and cast... depending on context.

In English, many words have different meanings depending on context: e.g. not to be mean, but you know what I mean, right? Ordinary human speakers have no problem with this, even without theoretical linguistic training.

I'm not convinced that Larry Wall (a formally trained linguist) has chosen meanings and contexts that really do fit in with what human speakers intuitively expect. But it could well be that it is just that I am personally familiar with C-style grammar, and not with Perl's. If I "grew up" with Perl, perhaps it would seem natural?

Perhaps it's exactly the same as with human languages: that languages with very different grammars are not so easy to learn for most people. And... perhaps there is a linguistic window for learning programming languages, as there is for human languages (which is up to about 7yo)?

masak8• 17 years ago

Oh, believe me, constructs in Perl (both Perl 5 and Perl 6) mean different things depending on context, too. :)

As a simple example, which you'll find in various languages, not just Perl: brackets ('[ ]') construct list objects when standing alone, but when they occur after something, they do array indexing into that thing. This all falls out naturally, and humans are very well equipped at switching between this type of contexts.

The Perl 5 behaviour of overloading 'reverse' with double meaning could be said to be context-dependent in this way. But the flip/reverse/invert distinction goes in the other direction, saying "hey, maybe we do want to keep these three concepts separate rather than crowding them all into the same method".

A similar thing has happened with 'length'. In Perl 5, 'length' always meant 'number of characters in the supplied string', but newbies kept expecting the function to work for lists too. It doesn't. In Perl 6, there's a method '.elems' for lists and '.chars' for strings. Neither of them are accessible as 'length'.

In a lot of places where Perl 5 overloads words and depends on context for the right semantics, Perl 6 strives to make things consistent and eliminate mental lists of things you have to remember.

tptacek5• 17 years ago

No, they mean different things depending on syntax. (char *) is never a function invocation.

10ren2• 17 years ago

I was picturing an AST, with the parentheses in the context of that. However, you're quite right that context seems to have a specific technical meaning here, and not the general one I was using.

nfnaaron2• 17 years ago

Interesting post about perl, but the end is most interesting about Life In General:

"But I guess there's also a moral to it all. We all start somewhere, and in a way it's reassuring to find five-year old proof of this fact. A newbie is just on a part of the learning curve you've already visited; they haven't had a chance to tweak their keyboard and developing environment to maximum efficiency yet, and they sometimes forget that the manual is there, or misread it in some way. So, don't hesitate to be be kind to them, and help them connect to the goodness that is perldoc, PerlMonks and Planet Iron Man so that they can grow and bloom into experienced wielders of Perl.

But don't hesitate to call them insane, either, when the situation calls for it."

The only thing missing from Life In General is The Fine Manual.

liquidben• 17 years ago

Reminds me of the mantra I repeat to myself whenever I start going to the gym again:

"Everybody's got to start somewhere"

nfnaaron2• 17 years ago

And that reminds me of an observation I made after going to the gym for a few months (and that after doing nothing for 30 years) :

I'm not good at anything, but I'm better at everything.

malkia• 17 years ago

Then I should no wonder I cannot program in Perl, and stick with Lisp, Lua, JavaScript & C.

masak8• 17 years ago

Perl 5 has many other sides apart from the context-dependence. To mention a few, the regex sublanguage is deeply integrated into the rest of the language, there's an active and versatile testing culture, and CPAN hosts 17k modules for countless of fields and applications.

Some of those (such as testing culture) are mirrored in other languages' cultures, others (such as CPAN) are unparalleled in scope. Ignoring Perl 5 based on a single feature causes you to miss out on all the truly good parts.

The taming of the newbie - a comedy on IRC

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