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Dec 10, 2022 at 20:16
Arrays being truthy in JS still catches me out sometimes. In Python or Lisp, empty lists are falsey and truthiness is safe and idiomatic.

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May 4, 2023 at 06:52
On storing ASTs in flat arrays for performance, and the relationship with bytecode interpreters:
Flattening ASTs (and Other Compiler Data Structures)
Flattening ASTs (and Other Compiler Data Structures)
This is an introduction to data structure flattening, a special case of arena allocation that is a good fit for programming language implementations. We build a simple interpreter twice, the normal way and the flat way, and show that some fairly mechanical code changes can give you a 2.4× speedup.
Jan 28, 2023 at 20:36
zsh is generally wonderful, and it's sufficiently like bash/POSIX sh that it works. However, it uses 1-indexed arrays, whereas bash uses 0-indexed arrays. This totally caught me out.
Sep 19, 2022 at 06:20
A decent part of VMs being faster than AST interpreters is just memory layout AIUI. VM instructions are largely flat arrays, so there's less pointer chasing.