strbuf
A growable string buffer for Carp. Provides
amortized O(1) appends, unlike String.append which allocates on every call.
Buffers are managed by Carp: an owned StringBuf is deleted when it goes out
of scope, so delete is never called by hand.
Usage
(defn greeting [name]
(let-do [sb (StringBuf.create)]
(StringBuf.append-str &sb "hello, ")
(StringBuf.append-str &sb name)
(StringBuf.into-string sb)))