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Everything Is Just Functions: 1 week with David Beazley and SICP

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389 points kurinikku | 1 comments | 17 Nov 24 15:07 UTC | HN request time: 0.209s | source
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liontwist ◴[17 Nov 24 16:26 UTC] No.42165013[source]▶
The cons/car/cdr implementation as lambda was magical the first time I saw it. But it just shows that the language runtime must implement key/value dictionaries and you are able to borrow that implementation to make other data structures.
replies(3): >>42165632 #>>42166573 #>>42203090 #
1. EuAndreh ◴[21 Nov 24 11:06 UTC] No.42203090[source]▶
Not key value dictionaries, just pointers are needed.

A closure with no behaviour is just a pointer to the enclosed variable. A closure with 2 pointers is a pair, which you can get the car and cdr.

The runtime needs to make the pointee available outside its definition, so escape analysis, garbage collection, etc. But no dictionary is needed.