(defun minimum (yourlist)
       (let ((min-i 0)
         (min-el (nth 0 yourlist)))
         (loop for el in yourlist
        for i from 0
        do (if (< el min-el)
               (progn
             (setf min-el el)
             (setf min-i i))))
         (values min-el min-i)))

    (defun pop-min (yourlist)
       (multiple-value-bind (min-el min-i) (minimum yourlist)
         (remove-if (lambda (x) t) yourlist :start min-i :end (1+ min-i))))