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27 lines
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1.2 KiB
Markdown
27 lines
No EOL
1.2 KiB
Markdown
# `debug.id`
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## Summary
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Add `debug.id` which accepts a value and always returns the identifier unique to that value.
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## Motivation
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When debugging, it is often useful to compare identity. Usually `print` will print the memory address of the table or userdata, but when `__tostring` is overriden, the address becomes unobtainable.
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`rawequal` can compare equality between two arguments, but is not suitable for a human comparing output between two `print` calls or between keys or values in a table.
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## Design
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`debug.id(value: string | userdata | table | thread | function): number` always returns the identifier unique to that value, and is not possible to override. The identifier can be reused after the value associated with it is garbage collected.
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While tables and userdata have individualized metatables, also allowing functions and threads to be passed to `debug.id` would let their type-level `__tostring` be redefined. Strings are useful to accept because of long, similar strings.
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## Drawbacks
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None known.
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## Alternatives
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Lua has `string.format("%p", {})`, but this is an invalid format option in Luau and less obvious.
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If not implemented, it remains annoying to compare identity when dealing with tables or userdata that override `__tostring`. |