Query Quantifiers

What you'll learn

• How ?, *, and + modify child matching.

Complete example

(expression (_) @x "+" @p (_) @y)   ; exactly two operands around one plus
(factor (number)?)                   ; a factor with an optional number child

How it works

• ? — the child may appear once at the current position or be absent.
• * — zero or more consecutive matching children (greedy).
• + — one or more consecutive matching children (greedy).
• Plain children match as an ordered subsequence: later pattern children may skip unmatched tree children, so (a b) finds b after a even with nodes in between.
• . anchors constrain the edges, ignoring anonymous nodes: a leading . pins the first child to the first named child, . between children requires named-adjacency, and a trailing . requires the last match to be the last named child. A . at group end is vacuous.
• !field asserts the node lacks a field: (pair !key) never matches a pair that binds key.

Repetition matching is greedy without full backtracking across the rest of the sequence; ambiguous patterns resolve to the longest greedy run. This covers the practical cases (optional nodes, repeated arguments) while keeping matching linear.

API used

• Query

Related guides

• Queries, Query Predicates