[plt-scheme] Mutable and immutable pairs in PLT Scheme

> typical in this respect --- "list" usually says "functional" to me,
> while "vector" usually says "imperative". That's why it's important for
> ...
> perspective affects a lot of my work on PLT Scheme, not only with
> immutable pairs, but also custodians, eventspaces, and designs for
> "kill safety", so I won't be swayed easily. :)

these are the attitudes that make PLT Scheme so cool, imhumbleiamnobodyo.

sincerely.