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Comment by weichi | Hacker News Reader

It's true that s-expressions don't give you a literal syntax for hashmaps or arrays, but note that some lisps (e.g. Clojure) do support these natively … and in a syntax that's better than JSON since you don't have to type all those annoying commas ;-)

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You know I never quite got that comma thing. For instance in python, the only reason it is necessary is because {"foo": "bar" "baz", 'k2':'v2'} is the same as {'foo':'barbaz', 'k2':'v2'}. Getting rid of auto-concatination allows for {'foo':'barbaz' 'k2':'v2'} which is pretty easy to parse base on tokens and ':'. It also eliminates a pretty common bug, in which there is kv pair per line, and the line ends with ',', except for the last line which does not have the ','. (The following line has a '}'). The common bug being adding a new kv pair and missing the ','.

Python lets you put the commas before the items, like so:

  { 'foo':'barbaz'
  , 'k2':'v2'
  }

Ruby doesn't like that though. Both Python and Ruby will ignore an extra trailing comma on the last item, which gives you another way of avoiding the common bug you describe.

I've never written any Ruby, but I refuse to believe that Ruby cares about which line has the comma. Am I misunderstanding something?

> It's true that s-expressions don't give you a literal syntax for hashmaps or arrays, but note that some lisps (e.g. Clojure

CL's reader is especially rich, and it's programmable....

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