How to use a closure as an argument of another closure?

[shelby3]

@jimb

The underlying problem here is that generic functions can't be values.

And my understanding is that is because Rust reifies generic functions per the caller's specification; whereas, for example Scala could reuse the same instance of a generic function because it employs type erasure instead of reification. I explained my understanding more as follows in other thread:

@shelby3

Agreed. The reason the example of this thread won't compile is not due to a lack of higher-kinded nor higher-ranked types, but rather because afaik the way Rust implements ad hoc polymorphism is it creates a separate instance of each function for each caller that uses a different set of input types, i.e. Rust's implementation is not a dynamic dispatch of passing in a hidden input argument for the dictionary for the trait implementation of the caller and is instead hard-coding the dictionary in each instance of the function, e.g. is not subclassing nor dynamic inversion-of-control ad hoc polymorphism (where the caller inputs the dictionary).

Please correct me if I am mistaken.