include require for exp2 for eigen var types

SteveBronder · SteveBronder · commit c73b8993cc30 · 2021-04-20T20:23:31.000-04:00
diff --git a/stan/math/rev/fun/exp2.hpp b/stan/math/rev/fun/exp2.hpp
@@ -41,7 +41,7 @@ inline var exp2(const var& a) {
   });
 }
 
-template <typename T>
+template <typename T, require_eigen_t<T>* = nullptr>
 inline auto exp2(const var_value<T>& a) {
   return make_callback_var(
       a.val().unaryExpr([](auto&& x) { return std::exp2(x); }),

Original file line number	Diff line number	Diff line change
`@@ -41,7 +41,7 @@ inline var exp2(const var& a) {`
`41`	`41`	`});`
`42`	`42`	`}`
`43`	`43`
`44`		`-template <typename T>`
	`44`	`+template <typename T, require_eigen_t<T>* = nullptr>`
`45`	`45`	`inline auto exp2(const var_value<T>& a) {`
`46`	`46`	`return make_callback_var(`
`47`	`47`	`a.val().unaryExpr([](auto&& x) { return std::exp2(x); }),`