Add let-expressions.
Remove overly general specialization of apply to avoid ambiguities.
Document the MetafunctionClass concept.
Add the curry metafunction class.
Document the Metafunction concept.
Accept a metafunction as the default for at_key.
Add transform and detail/adaptors.
Add filter and iterator_range.
Add join.
Replace vector_concat by join.
Rename curry to partial. It was not currying.
Add the compose MetafunctionClass.
Add benchmarks that were previously in gists.
Add the flip metafunction class.
Add a benchmark to compute fast sums.
Dismiss the possibility of returning a Maybe from at_key.
Update README.
Don't use lambda in all_of and any_of.