Never use any language feature that describes itself as "Smart" or "Magic."

http://www.expatsoftware.com/articles/2008/05/no-magic.html

by edw519 • 18 years ago

19 13 18 years ago

expatsoftware.com

sanj• 18 years ago

I would extend this law a little: if you're going to perform magic, it had better be absolutely flawless.

Otherwise, show what you're doing, or don't do it at all.

ericb• 18 years ago

I agree. This fits with Joel's law of leaky abstractions. Imperfect magic is dangerous. Perfect magic is wonderful.

http://www.joelonsoftware.com/articles/LeakyAbstractions.htm...

Rails pluralization rules are an interesting example, they leak--I have to know about exceptions, but they're consistent enough that they, in my opinion, just pass the threshold. Nearly-perfect magic is most tolerable when dealing with structure, not data and when the magic's imperfection is consistent, repeatable, and documented.

mtts• 18 years ago

Interesting example indeed. I'd say they are a perfect illustration of a feature that, in the words of the article author, "[tries] to abstract out some behavior that is not that hard to deal with anyway".

jrockway• 18 years ago

The logical conclusion of this article is that we should all design our own transistors, and program our apps in terms of the circuit that will execute them. That way nothing will trip us up along the way!

My reading of the article was "I didn't know how to use Hibernate or ActiveRecord, but I tried anyway, and they didn't work right." Yeah, that's the software's fault, not yours. Riiight.

As for magic_quotes, the problem was it was too general, not that it was too magical. Have you ever written this:

   run_query("SELECT * FROM foo WHERE foo=?", "'bar'")

Congratulations, the "'bar'" is magically quoted! It works because you are specifying exactly what you want quoted and why.

All in all, this has got to be one of the worst articles I've ever read in my life. And that is saying a lot.

Jesin• 18 years ago

Really? Do ads for transistors describe them as "smart" or "magic"?

The idea here is not that abstractions are bad, it's that those that are frequently described by the people who made them as "smart" or "magic" are often not very helpful, and tend to do more harm than good. There are some exceptions, but good abstractions, while they may be described as "smart", don't usually include that in their name, and are rarely if ever called "magic".

dgabriel2• 18 years ago

Neither ActiveRecord nor Hibernate have the words "smart," or "magic," in their names. They were bad examples.

The problem is not with these two packages, but with the developers who use them without taking the time to figure out exactly what they do. Just because something makes a task convenient or easy, does not mean you aren't required to understand how they work.

It's copy/paste, cargo-cult programming, and you can't blame the tools.

etal• 18 years ago

Using PHP's magic_quotes_runtime as an example can support pretty much any argument you want to make about software design choices. How about this: Don't rely on DWIM-style features to actually do what thought you meant. Just write what you mean.

Or, shorter: "Garbage in, garbage out."

cousin_it• 18 years ago

I remember Yegge calling Java's "smart" for-loop the "stupid" for-loop, and for good reasons.

http://steve.yegge.googlepages.com/next-big-thing

Never use any language feature that describes itself as "Smart" or "Magic."

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