MPL

mpl.lisp

(define-model wedding ()
    (possible-tables
     guests
     table-guests
     happiness
     max-tables)
  ;; variables
  (dvar 'x :binary
    (for i :in (param 'possible-tables)))
  ;; objective
  (minimize (sum (* (param 'happiness i) (var 'x i))
              (for i :in (param 'possible-tables))))
  ;; constraints
  (s.t. 'maximum-number-of-tables
    (<= (sum (var 'x i)
          (for i :in (param 'possible-tables)))
        (param 'max-tables)))
  (s.t. 'seat-each-guest-once
    (= (sum (var 'x i)
         (for i :in (param 'possible-tables))
         (where (member g (param 'table-guests i))))
       1)
    (for g :in (param 'guests))))
; => WEDDING

(make-instance 'wedding
  :possible-tables '(a b c d e)
  :guests '(alice bob carl)
  :table-guests '(a (alice bob) b (alice carl) c (bob carl) d (bob) e (carl))
  :happiness '(a 10 b 20 c 30 d 1 e 2)
  :max-tables 2)
; => #<WEDDING [MIN] 1 variable, 2 constraints @ #x1163ccea2>

(solve *)
; ...
; => #<MPL::SOLUTION 12.0 (optimal) @ #x112bb11d2>