Queries
Simple explanation
Queries find code by shape instead of text: "all identifiers inside binary expressions" rather than "the letters f-o-o". Patterns describe node types, parent-child nesting, and captured names; the engine returns every match with its captures.
Technical explanation
query/ compiles S-expression sources into flat pattern nodes (named / anonymous / wildcard kinds, field constraints, captures, quantifiers, anchors) plus predicates. Matching is a backtracking descent: roots match at any depth, children must be direct descendants in order, captures record into scratch space, and predicates filter afterwards. QueryCursor owns the collected matches. The matcher is generic over the same Language tables as the parser, so node-type checks respect named/anonymous distinctions.