## I think you forgot a parenthesis

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### 28 Responses:

1. colubra says:

nope: if we count from the left there're 3 left-parens, and then two right-parens. Then two left-parens, then 3 right-parens.
It still balances.

But I did have to double-check. ;)

• korgmeister says:

Wow! I thought it was just me who did that.

Did you keep track of opening and closing brackets using the fingers on each hand?

• colubra says:

It's not just you (but I used to copyedit for a living).
My trick is: count the left-parens as +1 and the right parens as -1.
So 1-2-3 2-1 2-3 2-1-0

I can see using one's hands working too, though!

• korgmeister says:

I like your technique! I'm going to use it, because I see it being pretty useful for when I'm debugging some of the more complicated mathematical functions.

• colubra says:

Thanks! It's always a huge pleasure to share something I've found works.

• I use the fingers method, myself.

But I would be totally amused by a Web site devoted to photos of tattoos wherein there were mistakes, with said mistakes copyedited in red Sharpie.

• lx says:

I counted the left parentheses. Then I counted the right parentheses.

Then I reflected on what I was doing.

• colubra says:

You were TOTALLY the smart one: welcome to me and my conditioned reflexes.

• Yep.

2. is that a quine?

that's a quine, isn't it?

• jwz says:

Do they click links on What?

3. benediktus says:

I'd rather...

• mackys says:

del dot B = 0 FTW!!!

• pozorvlak says:

Hurrah, a string of undefined symbols. Care to provide a link so those of us less versed in vector calculus can share the fun?

4. tjic says:

...doesn't seem to work on flesh buffers.

So, yeah, the old +1 / -1 trick.

• spike says:

Oh I don't know about that.
I seem to remember a few flesh-buffers I've forward-sexp'd.

*waits patiently for ensuing backward-sexp reference*

5. unpvg says:

So if you google around for it, it seems to be usually represented with fewer parens.
Like there http://en.wikipedia.org/wiki/Y_combinator

6. nightrider says:

See, at first glance I was thinking there were just misplaced perens midway through... but for once, I think someone on wikipedia may have known what they were talking about. I checked there and sure enough... that's the right one. But... (there's always a big but,) while Curry's combinator was the first discovered, there's definitely better combinators to geek out over.

If you're trying to get reduction to work with Curry's Y combinator, you're bound to run into problems. Reducing f (Y f) for example will require backwards beta reduction at some point. Teh suck.

Alan Turing's T combinator manages to avoid that issue, though:

T = (Î»x.Î»y.y (x x y)(Î»x.Î»y.y (x x y))

but my favorite one is this because it's the shortest one available when converted to the S and K basic combinators:

Y' = (Î».x.Î».y.xyx)(Î»x.Î»y.(x(Î».x.Î».y.xyx)yx)))

If it were me, I would have gotten the latter tattooed on my arm. It's worth *way* more geek points. I mean, Curry started it, but you have 12 terms in the final combinator as opposed to Curry's initial 18.

Ummm... Yeah.

• pozorvlak says:

I once met a guy at a Perl mongers' meeting who had Euclid's proof of Pythagoras' theorem tattooed on his upper arm. I got into a loud drunken argument with him over whether or not its historical significance outweighed its lack of elegance. I don't think either of us emerged from that argument with much dignity, but at least I didn't have an ugly proof permanently etched on my body.

7. kakos says:

Yikes. You freaked me out for a moment. The parens are all matched up correctly. As far as the correct number of parens, the extra parens I have as opposed to the wikipedia version doesn't really change anything with the formula. When I got the tattoo, the source I used to double check it used the extra parens.

As far as why I got this particular one instead of many of the other more elegant ones? Well, this is by far the most famous fixed-point combinator and it is far more iconic than many of the others.

8. hober says:

What's this obsession with the Y combinator. You people have no idea what you're dealing with. It'll eat you alive one day.

-- The Cube

• nightrider says:

I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration...

9. sckot says:

It'd be easier to add another paren than remove one.