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There are lots of [little to big] factual errors in this piece.

My favorite error is also rust related :

> Rust has no built-in support for immutable data structures.

This piece is flamebait.

I agree with your characterization of the article and had an initial head scratching with regard to that rust statement, in the context of the article it is correct. Rust certainly has built-in support for immutable data, it lacks what the author is calling ‘support for immutable data structures’. In particular, the author only seems to be considering support for persistent, immutable data structures, as referenced in all the functional language examples. Rust does not have any concept of an immutable list which is changed by simply adding a pointer to the unchanged part of the list to some new derived list. I think the author should have been more explicit in qualifying the immutable characteristic as persistent all the way through the article.

Arguably, the existence of Cell destroys any notion of immutability. It depends on your worldview; if an escape hatch of any kind makes immutability a lost cause, then this point has merit. But I don't see why that would be such a big deal, since the majority of the language is immutable by default.

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