#### 15.2.23 upgraded-array-element-type [Function]

`upgraded-array-element-type` typespec &optional environment ⇒ upgraded-typespec

#### Arguments and Values::

typespec—a type specifier.

environment—an environment object. The default is nil, denoting the null lexical environment and the current global environment.

upgraded-typespec—a type specifier.

#### Description::

Returns the element type of the most specialized array representation capable of holding items of the type denoted by typespec.

The typespec is a subtype of (and possibly type equivalent to) the upgraded-typespec.

If typespec is bit, the result is type equivalent to `bit`.

If typespec is base-char, the result is type equivalent to `base-char`.

If typespec is character, the result is type equivalent to `character`.

The purpose of upgraded-array-element-type is to reveal how an implementation does its upgrading.

The environment is used to expand any derived type specifiers that are mentioned in the typespec.

#### See Also::

array-element-type , make-array

#### Notes::

Except for storage allocation consequences and dealing correctly with the optional environment argument, upgraded-array-element-type could be defined as:

     (defun upgraded-array-element-type (type &optional environment)
       (array-element-type (make-array 0 :element-type type)))