Akar Function
Built-in function registry with scalar, aggregate, and table function dispatch.
Registered functions (259): 244 scalar + 14 aggregate + 1 table. Includes arithmetic, comparison, boolean, string, date/time, cast, list, map, struct, array, path, schema/utility, and 14 aggregates.
Custom function support:
CustomScalar— closure-based scalar functions via extension frameworkCustomTable— closure-based table functions
Aggregate state machine: AggValueState enum with Count, Sum, Avg, Min, Max, Collect
variants. Finalize() produces typed Value.
Tests: 182