diff --git a/headers/vmath.hpp/vmath_qua_fun.hpp b/headers/vmath.hpp/vmath_qua_fun.hpp
index 4f2c24d..b8f3280 100644
--- a/headers/vmath.hpp/vmath_qua_fun.hpp
+++ b/headers/vmath.hpp/vmath_qua_fun.hpp
@@ -13,6 +13,48 @@
 
 namespace vmath_hpp::detail::impl
 {
+    template < typename A, typename F, std::size_t... Is >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto map_join_impl(
+        F&& f,
+        const qua<A>& a,
+        std::index_sequence<Is...>
+    ) -> qua<decltype(f(
+        std::declval<A>()))>
+    {
+        return { f(a[Is])... };
+    }
+
+    template < typename A, typename B, typename F, std::size_t... Is >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto map_join_impl(
+        F&& f,
+        const qua<A>& a,
+        const qua<B>& b,
+        std::index_sequence<Is...>
+    ) -> qua<decltype(f(
+        std::declval<A>(),
+        std::declval<B>()))>
+    {
+        return { f(a[Is], b[Is])... };
+    }
+
+    template < typename A, typename B, typename C, typename F, std::size_t... Is >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto map_join_impl(
+        F&& f,
+        const qua<A>& a,
+        const qua<B>& b,
+        const qua<C>& c,
+        std::index_sequence<Is...>
+    ) -> qua<decltype(f(
+        std::declval<A>(),
+        std::declval<B>(),
+        std::declval<C>()))>
+    {
+        return { f(a[Is], b[Is], c[Is])... };
+    }
+
     template < typename A, typename B, typename F, std::size_t... Is >
     [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
     auto fold_join_impl(
@@ -35,10 +77,54 @@ namespace vmath_hpp::detail::impl
     ) -> A {
         return ((init = f(std::move(init), b[Is], c[Is])), ...);
     }
+
+    template < typename A, typename F, std::size_t I, std::size_t... Is >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto fold1_join_impl(
+        F&& f,
+        const qua<A>& a,
+        std::index_sequence<I, Is...>
+    ) -> A {
+        A init = a[I];
+        return ((init = f(std::move(init), a[Is])), ...);
+    }
 }
 
 namespace vmath_hpp::detail
 {
+    template < typename A, typename F >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto map_join(
+        F&& f,
+        const qua<A>& a
+    ) {
+        return impl::map_join_impl(
+            std::forward<F>(f), a, std::make_index_sequence<4>{});
+    }
+
+    template < typename A, typename B, typename F >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto map_join(
+        F&& f,
+        const qua<A>& a,
+        const qua<B>& b
+    ) {
+        return impl::map_join_impl(
+            std::forward<F>(f), a, b, std::make_index_sequence<4>{});
+    }
+
+    template < typename A, typename B, typename C, typename F >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto map_join(
+        F&& f,
+        const qua<A>& a,
+        const qua<B>& b,
+        const qua<C>& c
+    ) {
+        return impl::map_join_impl(
+            std::forward<F>(f), a, b, c, std::make_index_sequence<4>{});
+    }
+
     template < typename A, typename B, typename F >
     [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
     auto fold_join(
@@ -61,6 +147,16 @@ namespace vmath_hpp::detail
         return impl::fold_join_impl(
             std::forward<F>(f), std::move(init), b, c, std::make_index_sequence<4>{});
     }
+
+    template < typename A, typename F >
+    [[nodiscard]] constexpr VMATH_HPP_FORCE_INLINE
+    auto fold1_join(
+        F&& f,
+        const qua<A>& a
+    ) {
+        return impl::fold1_join_impl(
+            std::forward<F>(f), a, std::make_index_sequence<4>{});
+    }
 }
 
 //
diff --git a/untests/vmath_qua_fun_tests.cpp b/untests/vmath_qua_fun_tests.cpp
index dff5436..4f02c92 100644
--- a/untests/vmath_qua_fun_tests.cpp
+++ b/untests/vmath_qua_fun_tests.cpp
@@ -14,4 +14,29 @@ namespace
 }
 
 TEST_CASE("vmath/qua_fun") {
+    SUBCASE("Detail") {
+        STATIC_REQUIRE(map_join([](const int& x){
+            return x * 2;
+        }, qua(1,2,3,4)) == qua(2,4,6,8));
+
+        STATIC_REQUIRE(map_join([](const int& x, const int& y){
+            return x + y;
+        }, qua(1,2,3,4), qua(2,3,4,5)) == qua(3,5,7,9));
+
+        STATIC_REQUIRE(map_join([](const int& x, const int& y, const int& z){
+            return x + y + z;
+        }, qua(1,2,3,4), qua(2,3,4,5), qua(3,4,5,6)) == qua(6,9,12,15));
+
+        STATIC_REQUIRE(fold_join([](int acc, const int& x){
+            return acc + x;
+        }, 0, qua(1,2,3,4)) == 10);
+
+        STATIC_REQUIRE(fold_join([](int acc, const int& x, const int& y){
+            return acc + x + y;
+        }, 0, qua(1,2,3,4), qua(2,3,4,5)) == 24);
+
+        STATIC_REQUIRE(fold1_join([](const int& acc, const int& x){
+            return acc + x;
+        }, qua{1,2,3,4}) == 10);
+    }
 }