list - is not of the expected type `REAL' in Common LISP (CL) -

i made function , want make print :

(range ‘(0 7 8 2 3 –1))

(-1 8)

;; print 'the range between smallest number , second smallest number in list' , 'the largest number'

so made code :

(defun my-range (list-of-numbers)  (let* ((largest (max list-of-numbers))         (msmallest (min list-of-numbers))         (ssmallest (min (remove (min list-of-numbers) list-of-numbers)))         (range (- msmallest ssmallest)))   (list range largest)))  

and input function , number example on debug window :

(my-range '(0 7 8 2 3 -1))

error: (0 7 8 2 3 -1)' not of expected typereal'

[condition type: type-error]

the error message printed in window... meaning of 'is not of expected type 'real'? , how can fix problem? and, let me know problems code has?

i need help.