score-set

A #![no_std] + alloc Rust library for building weighted scoring operators — define metrics via a builder pipeline, combine them with weights into a zero-vtable flat scorer, and evaluate against any context.

Three concepts:

• Metric32<C, F> — a single named metric: measure closure + Map01 normalization
• score_set32! — macro that packs heterogeneous metrics into a flat tuple scorer
• Scored32<C, T> — the concrete scorer with .score(&C) and .breakdown(&C)

Quick example

use score_set::*;

struct Restaurant {
    cleanliness: f32,
    food_quality: f32,
}

// Define metrics — by() accepts closures (including capturing ones)
let clean = metric32("cleanliness")
    .measure()
    .by(|r: &Restaurant| r.cleanliness)
    .map01()
    .linear(100.0);

let food = metric32("food")
    .measure()
    .by(|r: &Restaurant| r.food_quality)
    .map01()
    .identity();

// Combine into a flat scorer (zero vtable, static dispatch)
let scorer = score_set32! { 2.0 => clean, 1.0 => food }?;

let r = Restaurant { cleanliness: 80.0, food_quality: 4.0 };
let total: f32 = scorer.score(&r);          // ~0.87

// Per-metric breakdown
let rows = scorer.breakdown(&r);
for row in rows {
    // row.name, row.raw, row.score, row.weight, row.contribution
}
# Ok::<(), &'static str>(())

Partial application (capturing closures)

let threshold: f32 = 0.6;
let quality = metric32("quality")
    .measure()
    .by(move |ctx: &MyCtx| if ctx.value > threshold { ctx.value } else { 0.0 })
    .map01()
    .identity();

// threshold is baked into the closure — scorer only needs &MyCtx
let scorer = score_set32! { 1.0 => quality }?;
let result = scorer.score(&ctx);

Precision

[dependencies]
score-set = "0.6"                                   # f32 only
score-set = { version = "0.6", features = ["f64"] }  # f64 only
score-set = { version = "0.6", features = ["both"] } # both

Building a metric

metric32("name")             // MetricNamingStage32
    .measure()               // MeasureStage32
    .by(|ctx| raw)           // MeasuredStage32<C, F>  — impl Fn(&C) -> f32
    .map01()                 // Map01Stage32<C, F>
    .<shape>(...)            // Metric32<C, F>

by() accepts any impl Fn(&C) -> f32 — function pointers, non-capturing closures, and capturing closures all work.

Map01 shapes

All variants (except Custom) guarantee output in [0, 1] by construction.

API

score_set32! — heterogeneous scorer

score_set32! { 2.0 => gc_metric, 1.0 => len_metric }?
//          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//          weight => metric pairs, comma-separated, up to 64 metrics

// Returns Result<Scored32<C, T>, &'static str>

Weights must be finite and strictly positive (> 0). The macro normalizes them to sum to 1 at construction time.

Scored32<C, T> — the concrete scorer

impl<C, T: ScoreSetTrait32<C>> Scored32<C, T> {
    /// Weighted sum over all metrics.
    pub fn score(&self, ctx: &C) -> f32;

    /// Per-metric breakdown rows.
    pub fn breakdown(&self, ctx: &C) -> Vec<Breakdown32>;
}

T is a flat tuple of Metric32<C, F> types — each F can be a different closure type. Trait dispatch is fully static (zero vtable).

Metric32<C, F> — single metric

pub struct Metric32<C, F = fn(&C) -> f32> {
    pub name: &'static str,
    // measure: F          (private)
    // map01: Map0132       (private)
}

impl<C, F: Fn(&C) -> f32> Metric32<C, F> {
    pub fn eval(&self, ctx: &C) -> Result<Witnessed<f32, Value01>, &'static str>;
    pub fn make_breakdown(&self, weight: f32, ctx: &C) -> Breakdown32;
}

Breakdown32

pub struct Breakdown32 {
    pub name: &'static str,
    pub raw: f32,           // original measured value
    pub score: f32,         // normalized, in [0, 1]
    pub weight: f32,        // normalized weight (sum = 1)
    pub contribution: f32,  // score × weight
}

Arity limits

By default, score_set32! supports up to 8 metrics. Enable higher arities via feature flags:

score-set = { version = "0.6", features = ["level-16"] }   # up to 16
score-set = { version = "0.6", features = ["level-32"] }   # up to 32
score-set = { version = "0.6", features = ["level-64"] }   # up to 64

Generated files (gen_score_set32.rs / gen_score_set64.rs) are maintained by cargo run -p xtask -- gen --max <N>.

no_std

This crate is #![no_std] with extern crate alloc. It only needs Vec from the allocator and libm for exp and log. Works on bare-metal targets.

License

MIT OR Apache-2.0