vector_norms.hpp

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/*
 * Copyright © 2025-2026 Akreon LLC
 * SPDX-License-Identifier: Apache-2.0
 */
 
#pragma once
 
#include "akreon/linalg/assert.hpp"
#include "akreon/linalg/linalg_ops.hpp"
#include "norm_traits.hpp"
 
namespace linalg {
 
template <FieldVector Vec>
struct L2 {
  using domain_type = remove_cvref_t<Vec>;
  using scalar_type = vector_element_t<domain_type>;
  using codomain_type = real_type_t<scalar_type>;
 
  constexpr codomain_type operator()(const domain_type& x) const {
    codomain_type result = 0;
    const auto squared_norm = inner_product(x, x);
    if constexpr (Real<scalar_type>) result = squared_norm;
    else {
      AK_ASSERT(is_real(squared_norm) &&
                "L2 complex norm expects real inner product");
      result = squared_norm.real();
    }
    return constexpr_sqrt_safe(result);
  }
};
 
template <FieldVector Vec>
struct L1 {
  using domain_type = remove_cvref_t<Vec>;
  using scalar_type = vector_element_t<domain_type>;
  using codomain_type = real_type_t<scalar_type>;
 
  constexpr codomain_type operator()(const domain_type& x) const {
    codomain_type sum = 0;
    for (const auto& _x : x) sum += constexpr_abs(_x);
    return sum;
  }
};
 
template <FieldVector Vec>
struct Linf {
  using domain_type = remove_cvref_t<Vec>;
  using scalar_type = vector_element_t<domain_type>;
  using codomain_type = real_type_t<scalar_type>;
 
  constexpr codomain_type operator()(const domain_type& x) const {
    codomain_type mx = 0;
    for (const auto& _x : x) mx = std::max(mx, constexpr_abs(_x));
    return mx;
  }
};
 
} // namespace linalg