anchor.diff:  			      :code-type :v-function)
   	     :initarg :flow-ids :reader flow-ids)))
   
  +(def-v-type-class v-function (v-type)
  +  ((versions :initform nil :initarg :versions :accessor v-versions)
  +   (argument-spec :initform nil :initarg :arg-spec :accessor v-argument-spec)
  +   (glsl-string :initform "" :initarg :glsl-string :reader v-glsl-string)
  +   (glsl-name :initarg :glsl-name :accessor v-glsl-name)
  +   (return-spec :initform nil :initarg :return-spec :accessor v-return-spec)
  +   (v-place-index :initform nil :initarg :v-place-index :reader v-place-index)
  +   (multi-return-vars :initform nil :initarg :multi-return-vars
  +                      :reader multi-return-vars)
  +   (name :initform nil :initarg :name :reader name)
  +   (implicit-args :initform nil :initarg :implicit-args :reader implicit-args)
  +   (in-arg-flow-ids :initform (error 'flow-ids-mandatory :for :v-function
  +				     :code-type :v-function)
  +		    :initarg :in-arg-flow-ids :reader in-arg-flow-ids)
  +   (flow-ids :initform (error 'flow-ids-mandatory :for :v-function
  +			      :code-type :v-function)
  +	     :initarg :flow-ids :reader flow-ids)))
  +
   (def-v-type-class v-user-function (v-function) ())
   
   (def-v-type-class v-stemcell (v-type) ())
  
positive.code:   (if (and (v-element-type type) (v-dimensions type))
        (list (type->type-spec (v-element-type type)) (v-dimensions type))
        'v-array))
  
  (defun try-type-spec->type (spec &key (env *global-env*))
    (declare (ignore env))
  
negative.code: 	     (when (or (typep type 'v-t-type)
  		       (typep type 'v-spec-type))
  	       type)))
            ((and (listp spec) (eq (first spec) 'function))
             (make-instance
              'v-func-val :arg-types (mapcar #'type-spec->type (second spec))
              :return-types (mapcar #'type-spec->type
                                    (uiop:ensure-list (third spec)))))
            ((and (listp spec) (vtype-existsp (first spec)))
             (destructuring-bind (type dimensions) spec
               (make-instance 'v-array :element-type (if (keywordp type)
  