Design Considerations

Select subtrees of collections.

A straightforward way to describe and create subselections of nested
collections.

# Design Considerations

## Clojury interface

Selectors should not look out of place in idiomatic clojure code;
selectors are plain data.

## General applicability

- Any combination of standard clojure collections and leaf nodes can
  be selected
  - Vectors (x number of items from the head)
  - Maps
  - Sets
  - Lists (x number of items from the head)

## Selected structure should be a "subtree" of the original

- Selected elements in a collection remain on the same key or index;
  paths to items in the collection remain valid in the selection.
- Selectors are unambiguous; the meaning of a selector does not depend
  on the structure of the tree.
- Selection of a collection will return the same kind of collection.
- Selection does not add keys to collections or extend sequential
  collections.
- Selection retains metadata.

## Selectors should be unambigious

- Paths in a selection can only be specified once, to prevent
  ambiguity.