What is lambda? [SOLVED]

Scripting Issues
1

I’ve explained before that I’m an artist and not a computer scientist, but for those who don’t know I’ve said it again.

There was a time when I was a nuclear engineer for the US Navy as well, but that’s more than half a decade behind me.

I am aware, thanks to wikipedia, that the greek letter lambda is used in some sort of calculus, but I’ve never learned calculus.

I was going through a camera handler script that I found on these forums (posted by Ninth) and I found the following:

self.accept("wheel_up",lambda : self.adjustCamDist(0.9))

And I thought to myself “I haven’t seen this sort of syntax before, a bold faced word followed by colon and a function… and what the duece is lambda?”

So I pose the question to all of you. What the duece is lambda?

2

The name is a bit misleading.

If you’re familiar with JavaScript, it’s the same as an ownerless function {} block.

Basically it’s just shorthand for saying, “I want a function here, but I don’t care for it to be named or owned by anything.”

You could re-write that as:

self.accept("wheel_up", yay_wheelUp)

def yay_wheelUp ():
  self.adjustCamDist(0.9)
3

Oh! How simple. That sounds all but identical to a functor, though there may be differences I don’t know of. I understand exactly what’s happening with that code now, thank you FenrirWolf.

4

Yeah, I see lambdas used a lot with map/reduce algorithms in Python, so I think it’s a handy stand in.

Someone who’s a bit more familiar with Python could tell you for sure though. :slight_smile:

5

I just thought lambda might be doing some foul Math thing to the values being fed to adjustCamDist.

If I learned anything from being a nuclear engineer, it’s that Math can’t be trusted. :smiley: