  The goal of unbounded program verification is to discover an inductive
invariant that safely over-approximates all possible program behaviors.
Functional languages featuring higher order and recursive functions become more
popular due to the domain-specific needs of big data analytics, web, and
security. We present Rosette/Unbound, the first program verifier for Racket
exploiting the automated constrained Horn solver on its backend. One of the key
features of Rosette/Unbound is the ability to synchronize recursive
computations over the same inputs allowing to verify programs that iterate over
unbounded data streams multiple times. Rosette/Unbound is successfully
evaluated on a set of non-trivial recursive and higher order functional
programs.
