fresnel integrals

[jorenham]

• fresnel
• modified_fresnel_plus
• modified_fresnel_minus

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See scipy/scipy#23558 for why the $K_-$ equation deviates from the one in SciPy's docstring.

[Copilot]

Pull Request Overview

This PR implements Fresnel integral functions for the mathematical special functions library. It adds three new functions: fresnel for computing standard Fresnel integrals, and modified_fresnel_plus/modified_fresnel_minus for computing modified Fresnel integrals.

• Adds standard Fresnel integral computation supporting both real and complex inputs
• Implements modified Fresnel positive and negative integral functions
• Extends test infrastructure to support tuple return types for the new functions

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/fresnel.rs	New module implementing Fresnel integral functions with trait-based dispatch
src/lib.rs	Exports the new Fresnel functions from the library
build.rs	Enables fresnel.h header and adds function bindings
tests/test_functions.rs	Adds test support for (f64, f64) and (Complex, Complex) return types

Comments suppressed due to low confidence (1)

src/fresnel.rs:1

• The format string assumes positive imaginary parts, but negative imaginary parts will display as +- (e.g., 1.0+-2.0i). Use {:+.6e} for the imaginary parts to handle signs correctly.

use crate::bindings;

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