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Discussion on: Should function arguments be reassignable or mutable?

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michelemauro profile image
michelemauro

In languages that manage memory for you (i.e. Java, or in general garbage collected runtimes), even if imperative, it's better to leave parameters as they are: the compiler may want to do some optimizations on their passing, and won't be able to if you modify them.
If you have a functional language, those optimizations are probably the norm, and you won't be able to do it at all (thus, you have one less problem to worry about).
If you have a runtime where you manage the memory directly (C, C++, or in embedded/IoT situations) there may be some circumstances where you're better off mutating your parameters; but you should be able to recognize them and use them correctly.

Otherwise, is much better to leave your parameters alone: they make the code much easier to reason about.

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mortoray profile image
edA‑qa mort‑ora‑y Author

Part of my motivation for the question was a defect in the Leaf compiler (my language). The fix is relatively simple, but it does imply an efficiency lost for calling functions.

As you say, if I limit what can be done with arguments by default, I gain a lot of flexibility in the compiler.