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Comment by tomp | Hacker News Reader

I understand map.

Here's the code I was trying to understand.

https://github.com/nakkaya/net-eval/blob/master/src/net_eval...

I'm not sure I do even now. I mean, I kinda know what different symbols and functions do, but I couldn't write it myself.

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I'm confused. Is it magical because you don't understand it, or do you not understand it because it's magical? It seems like you're saying the first one.

It's a (fairly simple) macro that defines a function which while doing so associates a quoted function definition (the same as the function being defined) with the metadata of the defined function's var: it might require a double reading (based on my inferior description) because it's got some meta-ness going on.

But the salient point here is there's really nothing magical about what's happening there.

Agreeing with everyone else here: there's no magic, but macros and metadata are fairly late topics in Clojure, and starting on a piece of code responsible for distributing code across a network... well, it wouldn't be my favourite place to start.

Of course, the power of Clojure is that you actually can express this concept in the language. RMI looks pretty ugly by comparison.

When you say full, of magic I think you mean the core langauge, witch is actually very simple. The example you provide is from a small test lib somewhere one github.

Lets look at the macro, once you understand the basic macro concepts, witch are actually quite simple but still hard to understand. Its like a normal function, exept that the function code will be added to the var as data.

If you understand clojure that code sample isn't hard to understand. Of course, I don't really know what it does, because reading 4 lines in a library without knowing anything else is always confusing.

It puts the code of a function into its metadata so that it can send it for remote evaluation easily (see fire-request below that extracts the :task metadata and sends it to a remote nrepl server).

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