The functional ones are taken from previous collections (SAS2011 and
OOPSLA13 submission for Sorting).

The imperative ones are based on testcases from the VSTTE competition
and adaptations of functional benchmarks of SAS.  We are not able to
reproduce all successfull properties of the functional benchmarks,
especially when the function we are implementating was not originally
tail recursive. In that case, a non-trivial encoding would be required
(e.g. using accumulators).

Insertion sort and other sort algorithms are particularly complicated to
implement with an imperative style. Functions like `insert` need to use
reversal while reconstructing the list, and need in particular to prove
that reversing an increasing list yields a decreasing list. We are not
able to prove that yet.

(Challenging benchmarks currently beyond our reach are in the top-level
testcases directory, as they are not part of the Scala 2013 submission.)