Fix vector handling in 3F2 and pFq

Author: andrjohns

stan/math/prim/fun/hypergeometric_3F2.hpp

@@ -118,7 +118,7 @@ inline auto hypergeometric_3F2(const Ta& a, const Tb& b, const Tz& z) {
   // Boost's pFq throws convergence errors in some cases, fallback to naive
   // infinite-sum approach (tests pass for these)
   if (z == 1.0 && (sum(b) - sum(a)) < 0.0) {
-    return internal::hypergeometric_3F2_infsum(a, b, z);
+    return internal::hypergeometric_3F2_infsum(to_vector(a), to_vector(b), z);
   }
   return hypergeometric_pFq(to_vector(a), to_vector(b), z);
 }

stan/math/prim/fun/hypergeometric_pFq.hpp

@@ -4,6 +4,7 @@
 #include <stan/math/prim/meta.hpp>
 #include <stan/math/prim/err/check_not_nan.hpp>
 #include <stan/math/prim/err/check_finite.hpp>
+#include <stan/math/prim/fun/to_row_vector.hpp>
 #include <boost/math/special_functions/hypergeometric_pFq.hpp>
 
 namespace stan {
@@ -14,10 +15,6 @@ namespace math {
  * input arguments:
  * \f$_pF_q(a_1,...,a_p;b_1,...,b_q;z)\f$
  *
- * This function is not intended to be exposed to end users, only
- * used for p & q values that are stable with the grad_pFq
- * implementation.
- *
  * See 'grad_pFq.hpp' for the derivatives wrt each parameter
  *
  * @param[in] a Vector of 'a' arguments to function
@@ -26,7 +23,7 @@ namespace math {
  * @return Generalized hypergeometric function
  */
 template <typename Ta, typename Tb, typename Tz,
-          require_all_eigen_st<std::is_arithmetic, Ta, Tb>* = nullptr,
+          require_all_vector_st<std::is_arithmetic, Ta, Tb>* = nullptr,
           require_arithmetic_t<Tz>* = nullptr>
 return_type_t<Ta, Tb, Tz> hypergeometric_pFq(const Ta& a, const Tb& b,
                                              const Tz& z) {
@@ -47,8 +44,9 @@ return_type_t<Ta, Tb, Tz> hypergeometric_pFq(const Ta& a, const Tb& b,
     std::stringstream msg;
     msg << "hypergeometric function pFq does not meet convergence "
         << "conditions with given arguments. "
-        << "a: " << a_ref << ", b: " << b_ref << ", "
-        << ", z: " << z;
+        << "a: " << to_row_vector(a_ref) << ", "
+        << "b: " << to_row_vector(b_ref) << ", "
+        << "z: " << z;
     throw std::domain_error(msg.str());
   }
 

test/unit/math/prim/fun/hypergeometric_3F2_test.cpp

@@ -3,9 +3,16 @@
 
 // converge
 TEST(MathPrimScalFun, F32_converges_by_z) {
-  EXPECT_NEAR(2.5,
-              stan::math::hypergeometric_3F2({1.0, 1.0, 1.0}, {1.0, 1.0}, 0.6),
-              1e-8);
+  using stan::math::hypergeometric_3F2;
+  using stan::math::to_vector;
+  using stan::math::to_row_vector;
+  std::vector<double> a = {1.0, 1.0, 1.0};
+  std::vector<double> b = {1.0, 1.0};
+  double z = 0.6;
+
+  EXPECT_NEAR(2.5, hypergeometric_3F2(a, b, z), 1e-8);
+  EXPECT_NEAR(2.5, hypergeometric_3F2(to_vector(a), to_vector(b), z), 1e-8);
+  EXPECT_NEAR(2.5, hypergeometric_3F2(to_row_vector(a), to_row_vector(b), z), 1e-8);
 }
 // terminate by zero numerator, no sign-flip
 TEST(MathPrimScalFun, F32_polynomial) {

test/unit/math/prim/fun/hypergeometric_pFq_test.cpp

@@ -4,6 +4,8 @@
 TEST(MathFunctions, hypergeometric_pFq_values) {
   using Eigen::VectorXd;
   using stan::math::hypergeometric_pFq;
+  using stan::math::to_array_1d;
+  using stan::math::to_row_vector;
 
   VectorXd a(2);
   VectorXd b(2);
@@ -12,6 +14,8 @@ TEST(MathFunctions, hypergeometric_pFq_values) {
   double z = 2;
 
   EXPECT_FLOAT_EQ(3.8420514314107791, hypergeometric_pFq(a, b, z));
+  EXPECT_FLOAT_EQ(3.8420514314107791, hypergeometric_pFq(to_row_vector(a), to_row_vector(b), z));
+  EXPECT_FLOAT_EQ(3.8420514314107791, hypergeometric_pFq(to_array_1d(a), to_array_1d(b), z));
 
   a << 6, 4;
   b << 3, 1;