[libcxx-commits] [libcxx] [libc++][math] Mathematical Special Functions: Hermite Polynomial (PR #89982)

[via libcxx-commits]

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@@ -0,0 +1,312 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+// <cmath>
+
+// Tests std::hermite and its related functions:
+//    double      hermite( unsigned n, double      x);
+//    float       hermite( unsigned n, float       x);
+//    long double hermite( unsigned n, long double x);
+//    float       hermitef(unsigned n, float       x);
+//    long double hermitel(unsigned n, long double x);
+//    template <class Integer>
+//    double      hermite( unsigned n, Integer     x);
+
+#include <array>
+#include <cassert>
+#include <cmath>
+#include <limits>
+#include <vector>
+
+#include "type_algorithms.h"
+
+inline constexpr unsigned MAX_N = 128;
+
+template <class T>
+std::array<T, 7> sample_points() {
+  return {-1.0, -0.5, -0.1, 0.0, 0.1, 0.5, 1.0};
+}
+
+template <class Real>
+class CompareFloatingValues {
+private:
+  Real abs_tol;
+  Real rel_tol;
+
+public:
+  CompareFloatingValues() {
+    abs_tol = []() -> Real {
+      if (std::is_same_v<Real, float>)
+        return 1e-5f;
+      else if (std::is_same_v<Real, double>)
+        return 1e-11;
+      else
+        return 1e-12l;
+    }();
+
+    rel_tol = abs_tol;
+  }
+
+  bool operator()(Real result, Real expected) const {
+    if (std::isinf(expected) && std::isinf(result))
+      return result == expected;
+
+    if (std::isnan(expected) || std::isnan(result))
+      return false;
+
+    Real tol = abs_tol + std::abs(expected) * rel_tol;
+    return std::abs(result - expected) < tol;
+  }
+};
+
+/// \note Roots are taken from
+/// Salzer, Herbert E., Ruth Zucker, and Ruth Capuano.
+/// Table of the zeros and weight factors of the first twenty Hermite
+/// polynomials. US Government Printing Office, 1952.
+template <class T>
+std::vector<T> get_roots(unsigned n) {
+  switch (n) {
+  case 0:
+    return {};
+  case 1:
+    return {T(0)};
----------------
PaulXiCao wrote:

I want to use the same style on this line as in the following ones. And the next lines need to perform a narrowing conversion (e.g. `return {T(0.707106781186548)};` for `T=float`). Using braces I assumed that the compiler or some tool (e.g. clang-tidy) would throw warnings. Let me know if this is baseless.

https://github.com/llvm/llvm-project/pull/89982