The Runtime Complexity (full) of the given CpxTRS could be proven to be BOUNDS(2^n, INF).

(0) Obligation:

Runtime Complexity TRS:
The TRS R consists of the following rules:

merge(nil, y) → y
merge(x, nil) → x
merge(.(x, y), .(u, v)) → if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
++(nil, y) → y
++(.(x, y), z) → .(x, ++(y, z))
if(true, x, y) → x
if(false, x, y) → x

Rewrite Strategy: FULL

(1) DecreasingLoopProof (EQUIVALENT transformation)

The following loop(s) give(s) rise to the lower bound Ω(2ⁿ):
The rewrite sequence
merge(.(x, y), .(u, v)) →⁺ if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
gives rise to a decreasing loop by considering the right hand sides subterm at position [1,1].
The pumping substitution is [y / .(x, y)].
The result substitution is [ ].

The rewrite sequence
merge(.(x, y), .(u, v)) →⁺ if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
gives rise to a decreasing loop by considering the right hand sides subterm at position [2,1].
The pumping substitution is [v / .(u, v)].
The result substitution is [ ].

(2) BOUNDS(2^n, INF)

(3) RenamingProof (EQUIVALENT transformation)

Renamed function symbols to avoid clashes with predefined symbol.

(4) Obligation:

Runtime Complexity Relative TRS:
The TRS R consists of the following rules:

merge(nil, y) → y
merge(x, nil) → x
merge(.(x, y), .(u, v)) → if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
++(nil, y) → y
++(.(x, y), z) → .(x, ++(y, z))
if(true, x, y) → x
if(false, x, y) → x

S is empty.
Rewrite Strategy: FULL

(5) TypeInferenceProof (BOTH BOUNDS(ID, ID) transformation)

Infered types.

(6) Obligation:

TRS:
Rules:
merge(nil, y) → y
merge(x, nil) → x
merge(.(x, y), .(u, v)) → if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
++(nil, y) → y
++(.(x, y), z) → .(x, ++(y, z))
if(true, x, y) → x
if(false, x, y) → x

Types:
merge :: nil:. → nil:. → nil:.
nil :: nil:.
. :: a → nil:. → nil:.
if :: <:true:false → nil:. → nil:. → nil:.
< :: a → a → <:true:false
++ :: nil:. → nil:. → nil:.
true :: <:true:false
false :: <:true:false
hole_nil:.1_0 :: nil:.
hole_a2_0 :: a
hole_<:true:false3_0 :: <:true:false
gen_nil:.4_0 :: Nat → nil:.

(7) OrderProof (LOWER BOUND(ID) transformation)

Heuristically decided to analyse the following defined symbols:
merge, ++

(8) Obligation:

TRS:
Rules:
merge(nil, y) → y
merge(x, nil) → x
merge(.(x, y), .(u, v)) → if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
++(nil, y) → y
++(.(x, y), z) → .(x, ++(y, z))
if(true, x, y) → x
if(false, x, y) → x

Types:
merge :: nil:. → nil:. → nil:.
nil :: nil:.
. :: a → nil:. → nil:.
if :: <:true:false → nil:. → nil:. → nil:.
< :: a → a → <:true:false
++ :: nil:. → nil:. → nil:.
true :: <:true:false
false :: <:true:false
hole_nil:.1_0 :: nil:.
hole_a2_0 :: a
hole_<:true:false3_0 :: <:true:false
gen_nil:.4_0 :: Nat → nil:.

Generator Equations:
gen_nil:.4_0(0) ⇔ nil
gen_nil:.4_0(+(x, 1)) ⇔ .(hole_a2_0, gen_nil:.4_0(x))

The following defined symbols remain to be analysed:
merge, ++

(9) NoRewriteLemmaProof (LOWER BOUND(ID) transformation)

Could not prove a rewrite lemma for the defined symbol merge.

(10) Obligation:

TRS:
Rules:
merge(nil, y) → y
merge(x, nil) → x
merge(.(x, y), .(u, v)) → if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
++(nil, y) → y
++(.(x, y), z) → .(x, ++(y, z))
if(true, x, y) → x
if(false, x, y) → x

Types:
merge :: nil:. → nil:. → nil:.
nil :: nil:.
. :: a → nil:. → nil:.
if :: <:true:false → nil:. → nil:. → nil:.
< :: a → a → <:true:false
++ :: nil:. → nil:. → nil:.
true :: <:true:false
false :: <:true:false
hole_nil:.1_0 :: nil:.
hole_a2_0 :: a
hole_<:true:false3_0 :: <:true:false
gen_nil:.4_0 :: Nat → nil:.

Generator Equations:
gen_nil:.4_0(0) ⇔ nil
gen_nil:.4_0(+(x, 1)) ⇔ .(hole_a2_0, gen_nil:.4_0(x))

The following defined symbols remain to be analysed:
++

(11) RewriteLemmaProof (LOWER BOUND(ID) transformation)

Proved the following rewrite lemma:
++(gen_nil:.4_0(n12126_0), gen_nil:.4_0(b)) → gen_nil:.4_0(+(n12126_0, b)), rt ∈ Ω(1 + n12126₀)

Induction Base:
++(gen_nil:.4_0(0), gen_nil:.4_0(b)) →_R^Ω(1)
gen_nil:.4_0(b)

Induction Step:
++(gen_nil:.4_0(+(n12126_0, 1)), gen_nil:.4_0(b)) →_R^Ω(1)
.(hole_a2_0, ++(gen_nil:.4_0(n12126_0), gen_nil:.4_0(b))) →_IH
.(hole_a2_0, gen_nil:.4_0(+(b, c12127_0)))

We have rt ∈ Ω(n¹) and sz ∈ O(n). Thus, we have irc_R ∈ Ω(n).

(12) Complex Obligation (BEST)

(13) Obligation:

TRS:
Rules:
merge(nil, y) → y
merge(x, nil) → x
merge(.(x, y), .(u, v)) → if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
++(nil, y) → y
++(.(x, y), z) → .(x, ++(y, z))
if(true, x, y) → x
if(false, x, y) → x

Types:
merge :: nil:. → nil:. → nil:.
nil :: nil:.
. :: a → nil:. → nil:.
if :: <:true:false → nil:. → nil:. → nil:.
< :: a → a → <:true:false
++ :: nil:. → nil:. → nil:.
true :: <:true:false
false :: <:true:false
hole_nil:.1_0 :: nil:.
hole_a2_0 :: a
hole_<:true:false3_0 :: <:true:false
gen_nil:.4_0 :: Nat → nil:.

Lemmas:
++(gen_nil:.4_0(n12126_0), gen_nil:.4_0(b)) → gen_nil:.4_0(+(n12126_0, b)), rt ∈ Ω(1 + n12126₀)

Generator Equations:
gen_nil:.4_0(0) ⇔ nil
gen_nil:.4_0(+(x, 1)) ⇔ .(hole_a2_0, gen_nil:.4_0(x))

No more defined symbols left to analyse.

(14) LowerBoundsProof (EQUIVALENT transformation)

The lowerbound Ω(n¹) was proven with the following lemma:
++(gen_nil:.4_0(n12126_0), gen_nil:.4_0(b)) → gen_nil:.4_0(+(n12126_0, b)), rt ∈ Ω(1 + n12126₀)

(15) BOUNDS(n^1, INF)

(16) Obligation:

TRS:
Rules:
merge(nil, y) → y
merge(x, nil) → x
merge(.(x, y), .(u, v)) → if(<(x, u), .(x, merge(y, .(u, v))), .(u, merge(.(x, y), v)))
++(nil, y) → y
++(.(x, y), z) → .(x, ++(y, z))
if(true, x, y) → x
if(false, x, y) → x

Types:
merge :: nil:. → nil:. → nil:.
nil :: nil:.
. :: a → nil:. → nil:.
if :: <:true:false → nil:. → nil:. → nil:.
< :: a → a → <:true:false
++ :: nil:. → nil:. → nil:.
true :: <:true:false
false :: <:true:false
hole_nil:.1_0 :: nil:.
hole_a2_0 :: a
hole_<:true:false3_0 :: <:true:false
gen_nil:.4_0 :: Nat → nil:.

Lemmas:
++(gen_nil:.4_0(n12126_0), gen_nil:.4_0(b)) → gen_nil:.4_0(+(n12126_0, b)), rt ∈ Ω(1 + n12126₀)

Generator Equations:
gen_nil:.4_0(0) ⇔ nil
gen_nil:.4_0(+(x, 1)) ⇔ .(hole_a2_0, gen_nil:.4_0(x))

No more defined symbols left to analyse.

(17) LowerBoundsProof (EQUIVALENT transformation)

The lowerbound Ω(n¹) was proven with the following lemma:
++(gen_nil:.4_0(n12126_0), gen_nil:.4_0(b)) → gen_nil:.4_0(+(n12126_0, b)), rt ∈ Ω(1 + n12126₀)

(18) BOUNDS(n^1, INF)