digamma_test.jule

// Copyright 2025 mertcandav.
// Use of this source code is governed by a BSD 3-Clause
// license that can be found in the LICENSE file.

use "std/math"
use "std/testing"

struct digammaTest {
	x:    f64
	want: f64
}

// Results computed using WolframAlpha.
let testsDigamma: []digammaTest = [
	{0.0, math::Inf(-1)},
	{math::Copysign(0.0, -1.0), math::Inf(1)},
	{math::Inf(1), math::Inf(1)},
	{math::Inf(-1), math::NaN()},
	{math::NaN(), math::NaN()},
	{-1.0, math::NaN()},
	{-100.5, 4.615124601338064117341315601525112558522917517910505881343},
	{0.5, -1.96351002602142347944097633299875556719315960466043},
	{10, 2.251752589066721107647456163885851537211808918028330369448},
	{math::Pow10(20), 46.05170185988091368035482909368728415202202143924212618733},
	{-1.111111111e9, math::NaN()},
	{1.46, -0.001580561987083417676105544023567034348339520110000},
]

#test
fn testDigamma(t: &testing::T) {
	for i, test in testsDigamma {
		got := Digamma(test.x)
		if !(math::IsNaN(got) && math::IsNaN(test.want)) &&
			!Tolerance(got, test.want, 1e-7) {
			t.Errorf("test {} Digamma({}) failed: got {} want {}", i, test.x, got, test.want)
		}
	}
}