MAYBE
* Step 1: Failure MAYBE
  + Considered Problem:
      - Strict TRS:
          APPEND(z0,z1) -> c4(IFAPPEND(z0,z1,is_empty(z0)),IS_EMPTY(z0))
          HD(cons(z0,z1)) -> c2()
          IFAPPEND(z0,z1,false()) -> c6(HD(z0))
          IFAPPEND(z0,z1,false()) -> c7(APPEND(tl(z0),z1),TL(z0))
          IFAPPEND(z0,z1,true()) -> c5()
          IS_EMPTY(cons(z0,z1)) -> c1()
          IS_EMPTY(nil()) -> c()
          TL(cons(z0,z1)) -> c3()
      - Weak TRS:
          append(z0,z1) -> ifappend(z0,z1,is_empty(z0))
          hd(cons(z0,z1)) -> z0
          ifappend(z0,z1,false()) -> cons(hd(z0),append(tl(z0),z1))
          ifappend(z0,z1,true()) -> z1
          is_empty(cons(z0,z1)) -> false()
          is_empty(nil()) -> true()
          tl(cons(z0,z1)) -> z1
      - Signature:
          {APPEND/2,HD/1,IFAPPEND/3,IS_EMPTY/1,TL/1,append/2,hd/1,ifappend/3,is_empty/1,tl/1} / {c/0,c1/0,c2/0,c3/0
          ,c4/2,c5/0,c6/1,c7/2,cons/2,false/0,nil/0,true/0}
      - Obligation:
          innermost runtime complexity wrt. defined symbols {APPEND,HD,IFAPPEND,IS_EMPTY,TL,append,hd,ifappend
          ,is_empty,tl} and constructors {c,c1,c2,c3,c4,c5,c6,c7,cons,false,nil,true}
  + Applied Processor:
      Sum {left = someStrategy, right = someStrategy}
  + Details:
      None
MAYBE