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This provides typesafe extension for sorted iterators to perform set and relational operations
It is possible to efficiently define set operations on sorted iterators. Sorted iterators are very common in the standard library. E.g. the elements of a [BTreeSet] or the keys of a [BTreeMap] are guaranteed to be sorted according to the element order.
There are also a number of operations on iterators that preserve the sort order. E.g. if an iterator is sorted, [take], [take_while] etc. are going to result in a sorted iterator as well.
Since the complete types of iterators are typically visible in rust, it is possible to encode these rules at type level. This is what this crate does.
Iterators of pairs that are sorted according to the first element / key are also very common in the standard library and elsewhere. E.g. the elements of a [BTreeMap] are guaranteed to be sorted according to the key order.
The same rules as for sorted iterators apply for preservation of the sort order, except that there are some additional operations that preserve sort order. Anything that only operates on the value, like e.g. map or filter_map on the value, is guaranteed to preserve the sort order.
The operations that can be defined on sorted pair operations are the relational operations known from relational algebra / SQL, namely join, leftjoin, rightjoin and outer_join.
Instances are provided to allow treating iterators in the standard library that are guaranteed to be sorted as sorted iterators.