Module util 

Shared helpers used across eval / vm:

• cmp_vals: total ordering on Val (null < bool < num < str < arr < obj), used by sort, min, max, top-N, distinct. Unlike PartialOrd, this never returns None — it uses a lexicographic fallback when types are incomparable, which is essential for heap-based partial sorts.
• add_vals / num_op: numeric widening + arithmetic dispatch shared by the tree-walker and the VM so both semantics match.
• val_key: canonical string key for grouping / dedup.
• flatten_val / zip_arrays / cartesian / deep_merge: array / object combinators reused by builtins.
• val_str / val_to_string: coercion helpers for string methods and CSV emission.

Functions

add_vals

cartesian

cmp_vals

deep_merge

deep_merge_concat

Deep-merge where arrays concatenate instead of replace. Used by the ...** spread operator. Objects recurse, arrays concat, scalars rhs-wins.

field_exists_nested

flatten_val

is_truthy

kind_matches

num_op

obj2

Build a Val::Obj with two string-key entries (common pattern for itertools output).

val_float

val_int

val_key

val_str

val_to_key

Canonical string key for use in HashSets / dedup (never allocates for Str).

val_to_string

vals_eq

zip_arrays