implement list.

i *think* it's correct, but i'm not quite sure. and even if it is
correct, is it a good way to implement it?

scm/evalo.scm

@@ -14,6 +14,16 @@
       [(== x y) (== v val)]
       [(=/= x y) (lookupo x rest val)]))))
(define evalmanyo
  (lambda (l env r)
    (conde
     [(== l '()) (== l r)]
     [(fresh (h t h^ t^)
        (== l `(,h  . ,t))
        (== r `(,h^ . ,t^))
        (evalo h env h^)
        (evalmanyo t env t^))])))
(define evalo
  (lambda (expr env val)
    (conde
@@ -22,6 +32,9 @@
     [(fresh (e)
        (== `(quote ,e) expr)
        (== e val))]
     [(fresh (els)
        (== `(list . ,els) expr)
        (evalmanyo els env val))]
     [(fresh (x body)
        (== `(lambda (,x) ,body) expr)
        (== `(closure ,x ,body ,env) val))]