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Comment by buddydvd | Hacker News Reader

Following the examples in the blog post, seems like the author would translate the following JSON expressions:

    {'a': 1}
    {'a': [1]}
    ['a' 1]
    ['a' [1]]

into this:

    ('a' 1)

Isn't that ambiguous? Or, do they need to be demarcated using special tokens (e.g. a for array and o for object) like this?

    {'a': 1}   => (o ('a' 1))
    {'a': [1]} => (o ('a' (a 1)))

If that's the case, nested arrays would require more characters to encode in S-expression than in JSON.

    ['a',['b',['c',['d',['e']]]]]

    (a 'a' (a 'b' (a 'c' (a 'd' (a 'e')))))

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You're correct, the major disadvantage here is the ambiguity not just in this JSON/S-expression translation but in any possible JSON/S-expression translation. Linear arrays and key-value dictionaries in most programming languages are intuitive and meaningful and usually even have a native data type. The conversion is usually very obvious. Not so much with S-expressions.

An even simpler problem is how do you express an empty array and an empty object in S-expressions? Is it () for both?

EDIT: and what about nulls? What about strings that resemble numbers?

Yes, there are certainly more problems. I think the reason why the author thought S-expressions are more compact is because the comparison was made between formatted versions of the expressions (how they would appear in code):

    ["a", "b", "c"]
    ("a" "b" "c")

Since people generally put spaces after their commas.

I did this in my code:

{'a': 1} -> (dict ('a' 1))

{'a': [1]} -> (dict ('a' (1)))

['a' 1] -> ('a' 1)

['a' [1]] -> ('a' (1))

['a',['b',['c',['d',['e']]]]] -> ('a' ('b' ('c' ('d' ('e')))))

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