1 #ifndef STAN_MATH_PRIM_FUN_FABS_HPP
2 #define STAN_MATH_PRIM_FUN_FABS_HPP
3
4 #include <stan/math/prim/meta.hpp>
5 #include <stan/math/prim/fun/Eigen.hpp>
6 #include <stan/math/prim/functor/apply_scalar_unary.hpp>
7 #include <stan/math/prim/functor/apply_vector_unary.hpp>
8 #include <cmath>
9
10 namespace stan {
11 namespace math {
12
13 template <typename T, require_arithmetic_t<T>* = nullptr>
fabs(T x)14 auto fabs(T x) {
15 return std::abs(x);
16 }
17
18 template <typename T, require_complex_t<T>* = nullptr>
fabs(T x)19 auto fabs(T x) {
20 return hypot(x.real(), x.imag());
21 }
22
23 /**
24 * Structure to wrap `fabs()` so that it can be vectorized.
25 *
26 * @tparam T type of variable
27 * @param x variable
28 * @return Absolute value of x.
29 */
30 struct fabs_fun {
31 template <typename T>
funstan::math::fabs_fun32 static inline T fun(const T& x) {
33 return fabs(x);
34 }
35 };
36
37 /**
38 * Returns the elementwise `fabs()` of the input,
39 * which may be a scalar or any Stan container of numeric scalars.
40 *
41 * @tparam Container type of container
42 * @param x container
43 * @return Absolute value of each value in x.
44 */
45 template <typename Container,
46 require_not_container_st<std::is_arithmetic, Container>* = nullptr,
47 require_not_var_matrix_t<Container>* = nullptr,
48 require_all_not_nonscalar_prim_or_rev_kernel_expression_t<
49 Container>* = nullptr,
50 require_not_stan_scalar_t<Container>* = nullptr>
fabs(const Container & x)51 inline auto fabs(const Container& x) {
52 return apply_scalar_unary<fabs_fun, Container>::apply(x);
53 }
54
55 /**
56 * Version of `fabs()` that accepts std::vectors, Eigen Matrix/Array objects
57 * or expressions, and containers of these.
58 *
59 * @tparam Container Type of x
60 * @param x Container
61 * @return Absolute value of each value in x.
62 */
63 template <typename Container,
64 require_container_st<std::is_arithmetic, Container>* = nullptr>
fabs(const Container & x)65 inline auto fabs(const Container& x) {
66 return apply_vector_unary<Container>::apply(
67 x, [](const auto& v) { return v.array().abs(); });
68 }
69
70 } // namespace math
71 } // namespace stan
72
73 #endif
74