The humble for loop in Rust

Re:The humble for loop in Rust by nuancebydefault on Friday December 13, 2024 @04:08PM (#42412368)

Java’s type erasure means that generic type information is not available at runtime.

C# lambdas: although non-capturing lambdas do not allocate, capturing lambdas do. "calls through them are virtual" is due to the underlying implementation of delegates in .NET.

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Re:The humble for loop in Rust by neonsunset on Friday December 13, 2024 @08:19PM (#42413824)

Well, yes, but delegates as a term is not often used in other languages so I did not mention them for simplicity's sake.

For what it's worth - the real issue in C# is not even the virtual calls but the way Roslyn caches lazily allocated non-capturing lambda instances. It does so in a compiler-unfriendly way due to questionable design decisions inside Roslyn.

Luckily, this has a high chance of changing in .NET 10. Ideally, by the time it releases hopefully the compiler will both understand the Roslyn's pattern of caching better and be able to stack-allocate non-escaping lambda closure instances.

Lambdas capturing 'this' inside instance methods of the object they refer to do not allocate either.

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