anchor.diff:      (error 'progn-special-form-must-be-proper-list
   	   :expr form))
     (make-instance 'progn-ast
  -		 :forms (loop for subform in (cdr form)
  -			      collect (convert subform environment))))
  +		 :forms (convert-sequence (cdr form) environment)))
   
   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;;;
  
positive.code: 			  environment)))
      (if (null binding)
  	(warn "undefined function: ~s" name)
  	(make-instance 'function-ast
  		       :binding binding
  		       :type (find-type binding environment)))))
  
  
negative.code: 	(make-instance 'function-call-ast
  		       :binding binding
  		       :type (find-type binding environment)
  		       :arguments (convert-sequence (cdr form) environment)))))
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;;
  