score-set

A #![no_std] + alloc Rust library for building weighted scoring operators — combine named metrics with weights, normalize, and produce a scoring function or breakdown.

Two public types are all you need:

ScoreSet<N> (builder): collect metrics → normalise weights → produce result
Metric<N> (single metric): fn(&C) -> Score measure + Map01 normalization

Where N is 32 (f32) or 64 (f64).

Quick example

use score_set::*;

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

// Define metrics via a builder pipeline
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 with weights → weighted-sum closure
let score = ScoreSet32::new()
    .push(2.0, clean)?
    .push(1.0, food)?
    .sum()?;

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

// Or get per-metric breakdown rows
let rows: Vec<Breakdown32> = ScoreSet32::new()
    .push(2.0, clean)?
    .push(1.0, food)?
    .breakdown(&r)?
    .into_iter()
    .collect();

for row in rows {
    // row.name, row.score, row.weight, row.contribution
}
# Ok::<(), &'static str>(())

Precision

Feature flag	Available types	Score type
(default)	`ScoreSet32`, `Metric32`, `metric32()`, …	`f32`
`f64`	`ScoreSet64`, `Metric64`, `metric64()`, …	`f64`
`both`	all of the above	both

[dependencies]
score-set = "0.3"                         # f32 only
score-set = { version = "0.3", features = ["f64"] }    # f64 only
score-set = { version = "0.3", features = ["both"] }   # both

Building a metric

metric32("name")           // MetricNamingStage32
    .measure()             // MeasureStage32
    .by(|ctx| raw)         // MeasuredStage32<C>  — fn pointer, no closures
    .map01()               // Map01Stage32<C>
    .<shape>(...)          // Metric32<C>

Map01 shapes

Shape	Constructor	Formula
Identity	`.identity()`	`raw.clamp(0, 1)`
Linear	`.linear(max)`	`raw / max`, clamped
Increasing sigmoid	`.inc_sigmoid(low, high)`	`1/(1 + e⁻ᵏ⁽ˣ⁻ᵐⁱᵈ⁾)`
Decreasing sigmoid	`.dec_sigmoid(low, high)`	`1/(1 + eᵏ⁽ˣ⁻ᵐⁱᵈ⁾)`
Cauchy (Lorentzian)	`.cauchy(center, scale)`	`1/(1 + ((x-c)/s)²)`
Custom	`.by(fn(Score) -> Score)`	user-provided

All variants (except Custom) guarantee output in [0, 1] by construction. Custom is validated at evaluation time via Value01 witness.

API

`ScoreSet<N>` — builder

ScoreSet32::new()                          // empty builder
    .push(weight, metric)?                 // add a metric (weight must be > 0, finite)
    .sum()?                                // → impl Fn(&C) -> Score
    .breakdown(&ctx)?                      // → impl IntoIterator<Item = Breakdown32>

sum() returns a closure — call it with any number of contexts.
breakdown() evaluates all metrics against one context, returns owned rows.

`Metric<N>` — single metric

pub struct Metric32<C> {
    pub name: &'static str,
    // measure: fn(&C) -> Score32  (private)
    // map01: Map0132              (private)
}

impl Metric32<C> {
    pub fn eval(&self, ctx: &C) -> Result<Witnessed<Score32, Value01>, &'static str>;
}

`Breakdown<N>`

pub struct Breakdown32 {
    pub name: &'static str,
    pub score: Score32,        // normalized, in [0, 1]
    pub weight: Score32,        // normalized weight (sum = 1)
    pub contribution: Score32,  // score × weight
}

`no_std`

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

License

MIT OR Apache-2.0

score-set 0.3.0