Trait RankingStrategy

Source

pub trait RankingStrategy {
    // Required methods
    fn policy_name(&self) -> &str;
    fn order(&self, frames: &[(String, ContextFrame)]) -> Vec<usize>;
}

Expand description

A host’s policy for ordering frames drawn from more than one provider — the choice SPEC.md §6.6 (F10) says a host owns and must name.

A strategy reports a permutation of the input indices, best first. It ranks; it never filters. Dropping evidence is the budget packer’s job in super::compose_for_prompt_with, which excludes a frame with a recorded ExclusionReason so the audit still explains every drop. A strategy that quietly returned fewer indices would put frames into neither the prompt nor the audit.

§Contract

order(frames) returns each index in 0..frames.len() exactly once.
The result depends only on frames as a set — not on their arrival order, and not on anything that varies between two runs over the same input. A HashMap iteration is the usual way to get this wrong.

rank_with holds the first half rather than trusting it: an index out of range or repeated is skipped, and any frame a strategy failed to place is appended in canonical order, so a third-party strategy cannot make the reference host lose evidence. It repairs rather than panicking — a library that aborted a host’s turn over a ranking bug would be a worse failure than the one it caught. is_ranking_permutation is the assertion to put in a strategy’s own tests.

Required Methods§

Source

fn policy_name(&self) -> &str

The policy’s name, for a host that has to state which cross-provider ordering it applied. F10 requires a host to document the choice; a strategy that cannot say what it is makes that impossible, which is why this has no default implementation.

Source