Crate cheby 

Chebyshev polynomial toolkit: node generation, coefficient fitting, and Clenshaw evaluation — generic over scalar type.

Overview

This crate provides the full pipeline for piecewise Chebyshev interpolation, as used in JPL DE-series ephemerides and cached lunar/planetary position evaluators:

1. nodes — Chebyshev node generation on [-1, 1] or mapped to an arbitrary interval.
2. [fit] — DCT-based coefficient computation from function values at Chebyshev nodes.
3. [eval] — Clenshaw-recurrence evaluation of a Chebyshev series (value, derivative, or both in one pass).
4. segment — Piecewise Chebyshev approximation over uniform time segments, with automatic lookup and t → τ normalisation.

All core functions are generic over ChebyScalar, so they work with raw f64 as well as typed quantities (qtty::Quantity<U>).

Re-exports

pub use scalar::ChebyScalar;

pub use segment::ChebySegment;

pub use segment::ChebySegmentTable;

Modules

scalar

Scalar trait for Chebyshev operations.

segment

Piecewise Chebyshev segment management.

Functions

evaluate

Evaluate a Chebyshev polynomial using the Clenshaw algorithm.

evaluate_both

Evaluate both the Chebyshev polynomial and its derivative in one pass.

evaluate_derivative

Evaluate the derivative of a Chebyshev polynomial.

fit_coeffs

Compute Chebyshev coefficients from function values at the canonical Chebyshev nodes.

fit_from_fn

Sample a function at N Chebyshev nodes on [start, end] and fit Chebyshev coefficients.

nodes

Compute N Chebyshev nodes on [-1, 1].

nodes_mapped

Compute N Chebyshev nodes mapped to the interval [start, end].