MAYBE
Input TRS:
      1: f(true(),xs) -> f(isList(xs),append(cons(a(),nil()),xs))
      2: isList(nil()) -> true()
      3: isList(cons(x,xs)) -> isList(xs)
      4: append(nil(),ys) -> ys
      5: append(cons(x,xs),ys) -> cons(x,append(xs,ys))
Number of strict rules: 5
Direct POLO(bPol) ... failed.
Uncurrying append
      1: f(true(),xs) -> f(isList(xs),append^1_cons(a(),nil(),xs))
      2: isList(nil()) -> true()
      3: isList(cons(x,xs)) -> isList(xs)
      4: append^1_nil(ys) -> ys
      5: append^1_cons(x,xs,ys) -> cons(x,append(xs,ys))
      6: append(cons(_1,_2),_3) ->= append^1_cons(_1,_2,_3)
      7: append(nil(),_1) ->= append^1_nil(_1)
Number of strict rules: 5
Direct POLO(bPol) ... failed.
Dependency Pairs:
     #1: #append(cons(_1,_2),_3) ->? #append^1_cons(_1,_2,_3)
     #2: #append(nil(),_1) ->? #append^1_nil(_1)
     #3: #append^1_cons(x,xs,ys) -> #append(xs,ys)
     #4: #isList(cons(x,xs)) -> #isList(xs)
     #5: #f(true(),xs) -> #f(isList(xs),append^1_cons(a(),nil(),xs))
     #6: #f(true(),xs) -> #isList(xs)
     #7: #f(true(),xs) -> #append^1_cons(a(),nil(),xs)
Number of SCCs: 3, DPs: 4
  SCC { #4 }
POLO(Sum)... succeeded.
      a 	w: 0
      append^1_cons	w: 0
      #append	w: 0
      #append^1_cons	w: 0
      #append^1_nil	w: 0
      true	w: 0
      f 	w: 0
      append	w: 0
      isList	w: 0
      nil	w: 0
      #f 	w: 0
      #isList	w: x1
      cons	w: x2 + 1
      append^1_nil	w: 0
    USABLE RULES: { }
    Removed DPs: #4
Number of SCCs: 2, DPs: 3
  SCC { #5 }
POLO(Sum)... POLO(max)... QLPOS... POLO(mSum)... QWPOpS(mSum)... Mat2b... failed.
Finding a loop...  failed.