[image] [ANN] First Release of ppx_pyformat 0.1.1 Community Using ^ for concatenation for each elements looks inefficient. Generating a call to String.concat "" should be more efficient and quite comparable in term of complexity for the code generator. I recently rece…

Let’s examine this code: let align_left w c s = let len = String.length s in if len >= w then s else s ^ String.make (w - len) c (* 1: 2 allocations + 2 copies *) The line marked 1 has 2 allocations: one for the new string, and one for the concatenation, and 2 copies: again, one for …

[image] bn-d: When the complier sees a chain of ^ operation, it will be automatically compiled to String.concat or something else similar. This would be a really bad thing to do, I think. There are many equations between different expressions, and starting to implement this sort of stuff is …

[image] Chet_Murthy: OCaml (and ML generally) has a history of being a language where you can look at what you wrote and know what it’s going to do. That means that whey you write a ^ b ^ c ^ d you’re expecting it to be three binary-concats, and left-to-right. You defeated your point as soon …

[image] bluddy: It’s also worth considering the Buffer module, which was created for exactly these kinds of use-cases. Buffer will force an additional allocation+copy on you at the end, because it doesn’t give you access to its internal bytes. So if you’re counting allocations, just stay away…

[image] c-cube: Buffer will force an additional allocation+copy on you at the end, because it doesn’t give you access to its internal bytes . So if you’re counting allocations, just stay away from it. Buffer is still useful when you want to build a string gradually but don’t want to compute h…

That’s true, that’s the use case. If you’re going to allocate a string eventually it’s fine to use Buffer.

Thanks! That is an excellent explanation! I totally overlooked the extra allocation and copy caused by Bytes.to_string in the second implementation. It is also good to know all the unsafe functions are actually available through the Stdlib.Bytes. I compared the performance of the function with bo…

Best practice for performant string operation?

Learning

mseri February 17, 2022, 9:46am 5

Tangentially related, have a look also at this thread for a discussion and benchmarks on the subject

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Best practice for performant string operation?

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