5 ms·

if Racket was built on top of immutable data structures, recursion, and the likes - why were imperative-like features such as mutation added to the language?

• capableweb 6y ago
  As I haven't used Racket for anything professionally, I can't really answer the question with Racket in mind. But Clojure is also built on top of immutable data structure, recursion and more, but also provides features for mutation of various things, both for pragmatism and sometimes performance. Clojure also lives like a hosted language (on top of JVM/browser engines/more), most of them being mutable by default, so providing those constructs help with interop as well.
• catalogia 6y ago
  It's not so much that mutation was added to racket. Racket started as a scheme, which has mutation. Some of that, like set-car! and set-cdr! were removed (cons cells were made immutable, though mcons was added for mutable cons cells) set! is one wasn't removed. I think removing set! would constitute a much more radical departure from scheme than what's been done already.
• neilv 6y ago
  Scheme was defined as an algorithmic language, not a strictly pure-functional one, though it also included some functional features and permitted other functional abstractions to be implemented. Racket slowly added some immutable data types to Scheme, which was a nice fit for some other Scheme features that had been there from the start, and better for software engineering (e.g., enforce that a user of a module couldn't go and mutate data you were sharing with them).
• sorawee 6y ago
  As a programmable programming language, I think it would be a shame if someone wants to use mutation and it's not available. On the other hand, if you don't want to use it, then don't use it! If you are a language creator that doesn't want your client to use variable mutation, you can even choose to not provide the construct very easily (see the Beginning Student Language which does exactly this).