The following works in sbcl+grid:

(copy-to (make-array 2 :element-type 'double-float :initial-contents '(1.0d0 2.0d0)) 'grid:foreign-array)

But it does not work in clisp+grid.

The root cause lies in the function grid/array.lisp/element-type. It uses `(array-element-type grid)'.

But this can present a problem. Quoting hyperspec:

(Because of array upgrading, this type specifier can in some cases denote a supertype of the expressed array element type of the array.)

In CLISP, array-element-type returns `T' when passed #(1d0 2d0)

It returns T even when passed a simple array:

(array-element-type (make-array 2 :element-type 'double-float :initial-contents
                      '(1.0d0 2.0d0)
                      :adjustable nil
                      :fill-pointer nil
                      :displaced-to nil) )

The proposed fix is

(defmethod element-type ((grid array))
(type-of (row-major-aref grid 0))
#+skip(array-element-type grid))

Now copy-to works in clisp as well.

Mirko