We are left with following problem, upon which TcT provides the
certificate YES(O(1),O(n^1)).

Strict Trs:
  { is_empty(nil()) -> true()
  , is_empty(cons(x, l)) -> false()
  , hd(cons(x, l)) -> x
  , tl(cons(x, l)) -> l
  , append(l1, l2) -> ifappend(l1, l2, l1)
  , ifappend(l1, l2, nil()) -> l2
  , ifappend(l1, l2, cons(x, l)) -> cons(x, append(l, l2)) }
Obligation:
  runtime complexity
Answer:
  YES(O(1),O(n^1))

We add the following weak dependency pairs:

Strict DPs:
  { is_empty^#(nil()) -> c_1()
  , is_empty^#(cons(x, l)) -> c_2()
  , hd^#(cons(x, l)) -> c_3(x)
  , tl^#(cons(x, l)) -> c_4(l)
  , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
  , ifappend^#(l1, l2, nil()) -> c_6(l2)
  , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }

and mark the set of starting terms.

We are left with following problem, upon which TcT provides the
certificate YES(O(1),O(n^1)).

Strict DPs:
  { is_empty^#(nil()) -> c_1()
  , is_empty^#(cons(x, l)) -> c_2()
  , hd^#(cons(x, l)) -> c_3(x)
  , tl^#(cons(x, l)) -> c_4(l)
  , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
  , ifappend^#(l1, l2, nil()) -> c_6(l2)
  , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
Strict Trs:
  { is_empty(nil()) -> true()
  , is_empty(cons(x, l)) -> false()
  , hd(cons(x, l)) -> x
  , tl(cons(x, l)) -> l
  , append(l1, l2) -> ifappend(l1, l2, l1)
  , ifappend(l1, l2, nil()) -> l2
  , ifappend(l1, l2, cons(x, l)) -> cons(x, append(l, l2)) }
Obligation:
  runtime complexity
Answer:
  YES(O(1),O(n^1))

No rule is usable, rules are removed from the input problem.

We are left with following problem, upon which TcT provides the
certificate YES(O(1),O(n^1)).

Strict DPs:
  { is_empty^#(nil()) -> c_1()
  , is_empty^#(cons(x, l)) -> c_2()
  , hd^#(cons(x, l)) -> c_3(x)
  , tl^#(cons(x, l)) -> c_4(l)
  , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
  , ifappend^#(l1, l2, nil()) -> c_6(l2)
  , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
Obligation:
  runtime complexity
Answer:
  YES(O(1),O(n^1))

The weightgap principle applies (using the following constant
growth matrix-interpretation)

The following argument positions are usable:
  Uargs(c_5) = {1}, Uargs(c_7) = {2}

TcT has computed the following constructor-restricted matrix
interpretation.

                     [nil] = [0]           
                             [0]           
                                           
            [cons](x1, x2) = [1 0] x2 + [0]
                             [0 1]      [0]
                                           
          [is_empty^#](x1) = [0]           
                             [0]           
                                           
                     [c_1] = [0]           
                             [0]           
                                           
                     [c_2] = [0]           
                             [0]           
                                           
                [hd^#](x1) = [1]           
                             [0]           
                                           
                 [c_3](x1) = [0]           
                             [0]           
                                           
                [tl^#](x1) = [0]           
                             [0]           
                                           
                 [c_4](x1) = [0]           
                             [0]           
                                           
        [append^#](x1, x2) = [2]           
                             [2]           
                                           
                 [c_5](x1) = [1 0] x1 + [0]
                             [0 1]      [0]
                                           
  [ifappend^#](x1, x2, x3) = [1]           
                             [0]           
                                           
                 [c_6](x1) = [0]           
                             [0]           
                                           
             [c_7](x1, x2) = [1 0] x2 + [2]
                             [0 1]      [2]

The order satisfies the following ordering constraints:

               [is_empty^#(nil())] =  [0]                          
                                      [0]                          
                                   >= [0]                          
                                      [0]                          
                                   =  [c_1()]                      
                                                                   
          [is_empty^#(cons(x, l))] =  [0]                          
                                      [0]                          
                                   >= [0]                          
                                      [0]                          
                                   =  [c_2()]                      
                                                                   
                [hd^#(cons(x, l))] =  [1]                          
                                      [0]                          
                                   >  [0]                          
                                      [0]                          
                                   =  [c_3(x)]                     
                                                                   
                [tl^#(cons(x, l))] =  [0]                          
                                      [0]                          
                                   >= [0]                          
                                      [0]                          
                                   =  [c_4(l)]                     
                                                                   
                [append^#(l1, l2)] =  [2]                          
                                      [2]                          
                                   >  [1]                          
                                      [0]                          
                                   =  [c_5(ifappend^#(l1, l2, l1))]
                                                                   
       [ifappend^#(l1, l2, nil())] =  [1]                          
                                      [0]                          
                                   >  [0]                          
                                      [0]                          
                                   =  [c_6(l2)]                    
                                                                   
  [ifappend^#(l1, l2, cons(x, l))] =  [1]                          
                                      [0]                          
                                   ?  [4]                          
                                      [4]                          
                                   =  [c_7(x, append^#(l, l2))]    
                                                                   

Further, it can be verified that all rules not oriented are covered by the weightgap condition.

We are left with following problem, upon which TcT provides the
certificate YES(?,O(n^1)).

Strict DPs:
  { is_empty^#(nil()) -> c_1()
  , is_empty^#(cons(x, l)) -> c_2()
  , tl^#(cons(x, l)) -> c_4(l)
  , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
Weak DPs:
  { hd^#(cons(x, l)) -> c_3(x)
  , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
  , ifappend^#(l1, l2, nil()) -> c_6(l2) }
Obligation:
  runtime complexity
Answer:
  YES(?,O(n^1))

We employ 'linear path analysis' using the following approximated
dependency graph:
->{3,7,6,5,4}                                [         ?          ]
   |
   |->{1}                                    [  YES(O(1),O(n^1))  ]
   |
   `->{2}                                    [  YES(O(1),O(n^1))  ]


Here dependency-pairs are as follows:

Strict DPs:
  { 1: is_empty^#(nil()) -> c_1()
  , 2: is_empty^#(cons(x, l)) -> c_2()
  , 3: tl^#(cons(x, l)) -> c_4(l)
  , 4: ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
Weak DPs:
  { 5: hd^#(cons(x, l)) -> c_3(x)
  , 6: append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
  , 7: ifappend^#(l1, l2, nil()) -> c_6(l2) }

* Path {3,7,6,5,4}->{1}: YES(O(1),O(n^1))
  ---------------------------------------
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(n^1)).
  
  Strict DPs:
    { is_empty^#(nil()) -> c_1()
    , tl^#(cons(x, l)) -> c_4(l)
    , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Weak DPs:
    { hd^#(cons(x, l)) -> c_3(x)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(n^1))
  
  We use the processor 'matrix interpretation of dimension 1' to
  orient following rules strictly.
  
  DPs:
    { 1: is_empty^#(nil()) -> c_1()
    , 2: tl^#(cons(x, l)) -> c_4(l)
    , 4: hd^#(cons(x, l)) -> c_3(x) }
  
  Sub-proof:
  ----------
    The following argument positions are usable:
      Uargs(c_5) = {1}, Uargs(c_7) = {2}
    
    TcT has computed the following constructor-based matrix
    interpretation satisfying not(EDA).
    
                         [nil] = [0]         
                                             
                [cons](x1, x2) = [1] x2 + [0]
                                             
              [is_empty^#](x1) = [5]         
                                             
                         [c_1] = [0]         
                                             
                    [hd^#](x1) = [1] x1 + [4]
                                             
                     [c_3](x1) = [0]         
                                             
                    [tl^#](x1) = [1] x1 + [4]
                                             
                     [c_4](x1) = [1] x1 + [0]
                                             
            [append^#](x1, x2) = [4] x1 + [0]
                                             
                     [c_5](x1) = [1] x1 + [0]
                                             
      [ifappend^#](x1, x2, x3) = [4] x3 + [0]
                                             
                     [c_6](x1) = [0]         
                                             
                 [c_7](x1, x2) = [1] x2 + [0]
    
    The order satisfies the following ordering constraints:
    
                   [is_empty^#(nil())] =  [5]                          
                                       >  [0]                          
                                       =  [c_1()]                      
                                                                       
                    [hd^#(cons(x, l))] =  [1] l + [4]                  
                                       >  [0]                          
                                       =  [c_3(x)]                     
                                                                       
                    [tl^#(cons(x, l))] =  [1] l + [4]                  
                                       >  [1] l + [0]                  
                                       =  [c_4(l)]                     
                                                                       
                    [append^#(l1, l2)] =  [4] l1 + [0]                 
                                       >= [4] l1 + [0]                 
                                       =  [c_5(ifappend^#(l1, l2, l1))]
                                                                       
           [ifappend^#(l1, l2, nil())] =  [0]                          
                                       >= [0]                          
                                       =  [c_6(l2)]                    
                                                                       
      [ifappend^#(l1, l2, cons(x, l))] =  [4] l + [0]                  
                                       >= [4] l + [0]                  
                                       =  [c_7(x, append^#(l, l2))]    
                                                                       
  
  The strictly oriented rules are moved into the weak component.
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(n^1)).
  
  Strict DPs:
    { ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Weak DPs:
    { is_empty^#(nil()) -> c_1()
    , hd^#(cons(x, l)) -> c_3(x)
    , tl^#(cons(x, l)) -> c_4(l)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(n^1))
  
  The following weak DPs constitute a sub-graph of the DG that is
  closed under successors. The DPs are removed.
  
  { is_empty^#(nil()) -> c_1() }
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(n^1)).
  
  Strict DPs:
    { ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Weak DPs:
    { hd^#(cons(x, l)) -> c_3(x)
    , tl^#(cons(x, l)) -> c_4(l)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(n^1))
  
  We use the processor 'matrix interpretation of dimension 1' to
  orient following rules strictly.
  
  DPs:
    { 1: ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2))
    , 2: hd^#(cons(x, l)) -> c_3(x)
    , 5: ifappend^#(l1, l2, nil()) -> c_6(l2) }
  
  Sub-proof:
  ----------
    The following argument positions are usable:
      Uargs(c_5) = {1}, Uargs(c_7) = {2}
    
    TcT has computed the following constructor-based matrix
    interpretation satisfying not(EDA).
    
                         [nil] = [0]         
                                             
                [cons](x1, x2) = [1] x2 + [1]
                                             
              [is_empty^#](x1) = [0]         
                                             
                         [c_1] = [0]         
                                             
                    [hd^#](x1) = [1] x1 + [0]
                                             
                     [c_3](x1) = [0]         
                                             
                    [tl^#](x1) = [0]         
                                             
                     [c_4](x1) = [0]         
                                             
            [append^#](x1, x2) = [4] x1 + [1]
                                             
                     [c_5](x1) = [1] x1 + [0]
                                             
      [ifappend^#](x1, x2, x3) = [4] x3 + [1]
                                             
                     [c_6](x1) = [0]         
                                             
                 [c_7](x1, x2) = [1] x2 + [2]
    
    The order satisfies the following ordering constraints:
    
                    [hd^#(cons(x, l))] =  [1] l + [1]                  
                                       >  [0]                          
                                       =  [c_3(x)]                     
                                                                       
                    [tl^#(cons(x, l))] =  [0]                          
                                       >= [0]                          
                                       =  [c_4(l)]                     
                                                                       
                    [append^#(l1, l2)] =  [4] l1 + [1]                 
                                       >= [4] l1 + [1]                 
                                       =  [c_5(ifappend^#(l1, l2, l1))]
                                                                       
           [ifappend^#(l1, l2, nil())] =  [1]                          
                                       >  [0]                          
                                       =  [c_6(l2)]                    
                                                                       
      [ifappend^#(l1, l2, cons(x, l))] =  [4] l + [5]                  
                                       >  [4] l + [3]                  
                                       =  [c_7(x, append^#(l, l2))]    
                                                                       
  
  The strictly oriented rules are moved into the weak component.
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(1)).
  
  Weak DPs:
    { hd^#(cons(x, l)) -> c_3(x)
    , tl^#(cons(x, l)) -> c_4(l)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2)
    , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(1))
  
  The following weak DPs constitute a sub-graph of the DG that is
  closed under successors. The DPs are removed.
  
  { hd^#(cons(x, l)) -> c_3(x)
  , tl^#(cons(x, l)) -> c_4(l)
  , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
  , ifappend^#(l1, l2, nil()) -> c_6(l2)
  , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(1)).
  
  Rules: Empty
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(1))
  
  Empty rules are trivially bounded

* Path {3,7,6,5,4}->{2}: YES(O(1),O(n^1))
  ---------------------------------------
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(n^1)).
  
  Strict DPs:
    { is_empty^#(cons(x, l)) -> c_2()
    , tl^#(cons(x, l)) -> c_4(l)
    , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Weak DPs:
    { hd^#(cons(x, l)) -> c_3(x)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(n^1))
  
  We use the processor 'matrix interpretation of dimension 1' to
  orient following rules strictly.
  
  DPs:
    { 1: is_empty^#(cons(x, l)) -> c_2()
    , 2: tl^#(cons(x, l)) -> c_4(l)
    , 4: hd^#(cons(x, l)) -> c_3(x) }
  
  Sub-proof:
  ----------
    The following argument positions are usable:
      Uargs(c_5) = {1}, Uargs(c_7) = {2}
    
    TcT has computed the following constructor-based matrix
    interpretation satisfying not(EDA).
    
                         [nil] = [0]         
                                             
                [cons](x1, x2) = [1] x2 + [0]
                                             
              [is_empty^#](x1) = [5]         
                                             
                         [c_2] = [1]         
                                             
                    [hd^#](x1) = [1] x1 + [4]
                                             
                     [c_3](x1) = [0]         
                                             
                    [tl^#](x1) = [1] x1 + [2]
                                             
                     [c_4](x1) = [1] x1 + [0]
                                             
            [append^#](x1, x2) = [4] x1 + [0]
                                             
                     [c_5](x1) = [1] x1 + [0]
                                             
      [ifappend^#](x1, x2, x3) = [4] x3 + [0]
                                             
                     [c_6](x1) = [0]         
                                             
                 [c_7](x1, x2) = [1] x2 + [0]
    
    The order satisfies the following ordering constraints:
    
              [is_empty^#(cons(x, l))] =  [5]                          
                                       >  [1]                          
                                       =  [c_2()]                      
                                                                       
                    [hd^#(cons(x, l))] =  [1] l + [4]                  
                                       >  [0]                          
                                       =  [c_3(x)]                     
                                                                       
                    [tl^#(cons(x, l))] =  [1] l + [2]                  
                                       >  [1] l + [0]                  
                                       =  [c_4(l)]                     
                                                                       
                    [append^#(l1, l2)] =  [4] l1 + [0]                 
                                       >= [4] l1 + [0]                 
                                       =  [c_5(ifappend^#(l1, l2, l1))]
                                                                       
           [ifappend^#(l1, l2, nil())] =  [0]                          
                                       >= [0]                          
                                       =  [c_6(l2)]                    
                                                                       
      [ifappend^#(l1, l2, cons(x, l))] =  [4] l + [0]                  
                                       >= [4] l + [0]                  
                                       =  [c_7(x, append^#(l, l2))]    
                                                                       
  
  The strictly oriented rules are moved into the weak component.
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(n^1)).
  
  Strict DPs:
    { ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Weak DPs:
    { is_empty^#(cons(x, l)) -> c_2()
    , hd^#(cons(x, l)) -> c_3(x)
    , tl^#(cons(x, l)) -> c_4(l)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(n^1))
  
  The following weak DPs constitute a sub-graph of the DG that is
  closed under successors. The DPs are removed.
  
  { is_empty^#(cons(x, l)) -> c_2() }
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(n^1)).
  
  Strict DPs:
    { ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Weak DPs:
    { hd^#(cons(x, l)) -> c_3(x)
    , tl^#(cons(x, l)) -> c_4(l)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(n^1))
  
  We use the processor 'matrix interpretation of dimension 1' to
  orient following rules strictly.
  
  DPs:
    { 1: ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2))
    , 2: hd^#(cons(x, l)) -> c_3(x)
    , 5: ifappend^#(l1, l2, nil()) -> c_6(l2) }
  
  Sub-proof:
  ----------
    The following argument positions are usable:
      Uargs(c_5) = {1}, Uargs(c_7) = {2}
    
    TcT has computed the following constructor-based matrix
    interpretation satisfying not(EDA).
    
                         [nil] = [0]         
                                             
                [cons](x1, x2) = [1] x2 + [1]
                                             
              [is_empty^#](x1) = [0]         
                                             
                         [c_2] = [0]         
                                             
                    [hd^#](x1) = [1] x1 + [0]
                                             
                     [c_3](x1) = [0]         
                                             
                    [tl^#](x1) = [0]         
                                             
                     [c_4](x1) = [0]         
                                             
            [append^#](x1, x2) = [4] x1 + [1]
                                             
                     [c_5](x1) = [1] x1 + [0]
                                             
      [ifappend^#](x1, x2, x3) = [4] x3 + [1]
                                             
                     [c_6](x1) = [0]         
                                             
                 [c_7](x1, x2) = [1] x2 + [2]
    
    The order satisfies the following ordering constraints:
    
                    [hd^#(cons(x, l))] =  [1] l + [1]                  
                                       >  [0]                          
                                       =  [c_3(x)]                     
                                                                       
                    [tl^#(cons(x, l))] =  [0]                          
                                       >= [0]                          
                                       =  [c_4(l)]                     
                                                                       
                    [append^#(l1, l2)] =  [4] l1 + [1]                 
                                       >= [4] l1 + [1]                 
                                       =  [c_5(ifappend^#(l1, l2, l1))]
                                                                       
           [ifappend^#(l1, l2, nil())] =  [1]                          
                                       >  [0]                          
                                       =  [c_6(l2)]                    
                                                                       
      [ifappend^#(l1, l2, cons(x, l))] =  [4] l + [5]                  
                                       >  [4] l + [3]                  
                                       =  [c_7(x, append^#(l, l2))]    
                                                                       
  
  The strictly oriented rules are moved into the weak component.
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(1)).
  
  Weak DPs:
    { hd^#(cons(x, l)) -> c_3(x)
    , tl^#(cons(x, l)) -> c_4(l)
    , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
    , ifappend^#(l1, l2, nil()) -> c_6(l2)
    , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(1))
  
  The following weak DPs constitute a sub-graph of the DG that is
  closed under successors. The DPs are removed.
  
  { hd^#(cons(x, l)) -> c_3(x)
  , tl^#(cons(x, l)) -> c_4(l)
  , append^#(l1, l2) -> c_5(ifappend^#(l1, l2, l1))
  , ifappend^#(l1, l2, nil()) -> c_6(l2)
  , ifappend^#(l1, l2, cons(x, l)) -> c_7(x, append^#(l, l2)) }
  
  We are left with following problem, upon which TcT provides the
  certificate YES(O(1),O(1)).
  
  Rules: Empty
  Obligation:
    runtime complexity
  Answer:
    YES(O(1),O(1))
  
  Empty rules are trivially bounded

Hurray, we answered YES(O(1),O(n^1))