# Standard Libraries vs Tail-Recursion

**URL:** <https://forum.elixirforum.com/t/standard-libraries-vs-tail-recursion/46673>\
**Category:** Questions\
**Tags:** performance, tail-call\
**Created:** [March 18, 2022, 3:13pm UTC](https://forum.elixirforum.com/t/standard-libraries-vs-tail-recursion/46673 "2022-03-18T15:13:19Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![al2o3cr](https://forum.elixirforum.com/user_avatar/forum.elixirforum.com/al2o3cr/32/3457_2.png) [@al2o3cr](https://forum.elixirforum.com/u/al2o3cr)\
**Post date:** [March 18, 2022, 6:00pm UTC](https://forum.elixirforum.com/t/standard-libraries-vs-tail-recursion/46673/6 "2022-03-18T18:00:47Z")

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Looks like `String.downcase` reassembles the string from individual codepoints:

> <https://github.com/elixir-lang/elixir/blob/18c44e2e4fb6cfe00f04eb0117f648bb57227c8c/lib/elixir/unicode/unicode.ex#L295>

That should lose any reference to the original un-`split` binary, right?

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