Re: Function ARRAY-ELEMENT-TYPE

In article 
<96353525-4cf6-4cdf-b02a-09159e43252b@[EMAIL PROTECTED]
>,
 danb <sogwaldan@[EMAIL PROTECTED]
> wrote:

> * (array-element-type (MAKE-ARRAY '(2)
>                  :ELEMENT-TYPE 'INTEGER
>                  :INITIAL-CONTENTS '(1 2)))
> => T
> 
> Why does this function exist?  It doesn't seem to do much.

Which function? array-element-type ?
It returns the type T in your example. That's fine.

Your Lisp has decided that the element type of
the above array is of type T. Means it
does not have a special array type for
arrays with element type INTEGER.

Read about Array Upgrading:
http://www.lisp.org/HyperSpec/Body/sec_15-1-2-1.html

Here is an example where a Lisp does not upgrade an
element type:

? (array-element-type (MAKE-ARRAY '(2)
                 :ELEMENT-TYPE 'fixnum
                 :INITIAL-CONTENTS '(1 2)))
FIXNUM

See also these examples:

? (array-element-type (MAKE-ARRAY '(2)
                 :ELEMENT-TYPE '(unsigned-byte 4)
                 :INITIAL-CONTENTS '(1 2)))
(UNSIGNED-BYTE 8)

? (array-element-type (MAKE-ARRAY '(2)
                 :ELEMENT-TYPE '(unsigned-byte 9)
                 :INITIAL-CONTENTS '(1 2)))
(UNSIGNED-BYTE 16)


 
> 
> --Dan
> 
> ------------------------------------------------
> Dan Bensen
> http://www.prairienet.org/~dsb/
> 
> cl-match:  expressive pattern matching in Lisp
> http://common-lisp.net/project/cl-match/

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