fix directory structure

source/libs/array/to_array.rst

@@ -0,0 +1,39 @@
+.. _sprout-array-to_array:
+###############################################################################
+to_array
+###############################################################################
+
+Interface
+========================================
+.. sourcecode:: c++
+
+  template<typename T, std::size_t N>
+  inline SPROUT_CONSTEXPR sprout::array<T, N>
+  to_array(T const (& arr)[N]);
+
+Returns
+========================================
+
+| Returns the array object copied all elements from the built-in array.
+
+Examples
+========================================
+.. sourcecode:: c++
+
+  #include <sprout/array.hpp>
+  
+  SPROUT_STATIC_CONSTEXPR int x[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  SPROUT_STATIC_CONSTEXPR auto y = sprout::to_array(x);
+  static_assert(y[0] == x[0], "array y is same as built-in array x.");
+
+Complexity
+========================================
+
+| Recursive function invocations in *O(1)* (constant) depth.
+
+Header
+========================================
+
+| ``sprout/array/array.hpp``
+| Convenience header: ``sprout/array.hpp``
+