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Phi.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_FUN_PHI_HPP
2 #define STAN_MATH_PRIM_SCAL_FUN_PHI_HPP
3
4 #include <boost/math/tools/promotion.hpp>
5 #include <boost/math/special_functions/erf.hpp>
6 #include <stan/math/prim/scal/fun/constants.hpp>
7 #include <stan/math/prim/scal/err/check_not_nan.hpp>
8
9 namespace stan {
10 namespace math {
11
29 template <typename T>
30 inline typename boost::math::tools::promote_args<T>::type
31 Phi(const T x) {
32 // overridden in fvar and var, so can hard-code boost versions
33 // here for scalars only
34 using stan::math::check_not_nan;
35
36 check_not_nan("Phi", "x", x);
37 if (x < -37.5)
38 return 0;
39 else if (x < -5.0)
40 return 0.5 * boost::math::erfc(-INV_SQRT_2 * x);
41 else if (x > 8.25)
42 return 1;
43 else
44 return 0.5 * (1.0 + boost::math::erf(INV_SQRT_2 * x));
45 }
46
47 }
48 }
49
50 #endif
check_not_nan.hpp
stan::math::check_not_nan
bool check_not_nan(const char *function, const char *name, const T_y &y)
Return true if y is not NaN.
Definition: check_not_nan.hpp:63
stan::math::erf
fvar< T > erf(const fvar< T > &x)
Definition: erf.hpp:14
stan::math::INV_SQRT_2
const double INV_SQRT_2
The value of 1 over the square root of 2, .
Definition: constants.hpp:27
stan::math::Phi
fvar< T > Phi(const fvar< T > &x)
Definition: Phi.hpp:14
constants.hpp
stan::math::erfc
fvar< T > erfc(const fvar< T > &x)
Definition: erfc.hpp:14

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