Vector aggregates

pub fn min_of < T: Ordered > (v: vector<T>) -> T?

Smallest element in a vector, or null when the vector is empty (@PLN102 keystone step 4 — the type is honest about the empty case). Works on any Ordered type (op <). Example: @STD-004

pub fn max_of < T: Ordered > (v: vector<T>) -> T?

Largest element in a vector, or null when the vector is empty (@PLN102 keystone step 4 — the type is honest about the empty case). Works on any Ordered type (op <). Example: @STD-004

pub fn sum < T: Addable > (v: vector<T>, init: T) -> T

Sum of vector elements with caller-supplied identity. Works on any Addable type. Example: sum([10, 20, 12], 0) == 42 Example: @STD-005

pub fn sum_of(v: vector<integer>) -> integer

Sum of all integer elements. Returns 0 for an empty vector. @PLN102 arc C — superseded by the general `sum(v, init)`; kept as a shim over it (the old form keeps working). `sum_of(v)` == `sum(v, 0)`. Defined AFTER `sum` so the shim's call resolves — a forward reference to a generic is not yet supported.

pub fn tree_walk < T: Walkable > (wk_root: T, cap: integer) -> vector<T>

Example: @STD-006