Term Rewriting System R:
[x, y, w, z]
app(app(lt, app(s, x)), app(s, y)) -> app(app(lt, x), y)
app(app(lt, 0), app(s, y)) -> true
app(app(lt, y), 0) -> false
app(app(eq, x), x) -> true
app(app(eq, app(s, x)), 0) -> false
app(app(eq, 0), app(s, x)) -> false
app(app(member, w), null) -> false
app(app(member, w), app(app(app(fork, x), y), z)) -> app(app(app(if, app(app(lt, w), y)), app(app(member, w), x)), app(app(app(if, app(app(eq, w), y)), true), app(app(member, w), z)))

Termination of R to be shown. 



   R
     ↳Overlay and local confluence Check



The TRS is overlay and locally confluent (all critical pairs are trivially joinable).Hence, we can switch to innermost. 


   R
     ↳OC
       →TRS2
         ↳Dependency Pair Analysis



R contains the following Dependency Pairs:

APP(app(lt, app(s, x)), app(s, y)) -> APP(app(lt, x), y)
APP(app(lt, app(s, x)), app(s, y)) -> APP(lt, x)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(app(if, app(app(lt, w), y)), app(app(member, w), x)), app(app(app(if, app(app(eq, w), y)), true), app(app(member, w), z)))
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(if, app(app(lt, w), y)), app(app(member, w), x))
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(if, app(app(lt, w), y))
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(lt, w), y)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(lt, w)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(member, w), x)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(app(if, app(app(eq, w), y)), true), app(app(member, w), z))
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(if, app(app(eq, w), y)), true)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(if, app(app(eq, w), y))
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(eq, w), y)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(eq, w)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(member, w), z)

Furthermore, R contains two SCCs. 


   R
     ↳OC
       →TRS2
         ↳DPs
           →DP Problem 1
             ↳Usable Rules (Innermost)
           →DP Problem 2
             ↳UsableRules


Dependency Pair:

APP(app(lt, app(s, x)), app(s, y)) -> APP(app(lt, x), y)


Rules:


app(app(lt, app(s, x)), app(s, y)) -> app(app(lt, x), y)
app(app(lt, 0), app(s, y)) -> true
app(app(lt, y), 0) -> false
app(app(eq, x), x) -> true
app(app(eq, app(s, x)), 0) -> false
app(app(eq, 0), app(s, x)) -> false
app(app(member, w), null) -> false
app(app(member, w), app(app(app(fork, x), y), z)) -> app(app(app(if, app(app(lt, w), y)), app(app(member, w), x)), app(app(app(if, app(app(eq, w), y)), true), app(app(member, w), z)))


Strategy:

innermost




As we are in the innermost case, we can delete all 8 non-usable-rules.


   R
     ↳OC
       →TRS2
         ↳DPs
           →DP Problem 1
             ↳UsableRules
             ...
               →DP Problem 3
                 ↳A-Transformation
           →DP Problem 2
             ↳UsableRules


Dependency Pair:

APP(app(lt, app(s, x)), app(s, y)) -> APP(app(lt, x), y)


Rule:

none


Strategy:

innermost




We have an applicative DP problem with proper arity. Thus we can use the A-Transformation to obtain one new DP problem which consists of the A-transformed TRSs.


   R
     ↳OC
       →TRS2
         ↳DPs
           →DP Problem 1
             ↳UsableRules
             ...
               →DP Problem 4
                 ↳Size-Change Principle
           →DP Problem 2
             ↳UsableRules


Dependency Pair:

LT(s(x), s(y)) -> LT(x, y)


Rule:

none


Strategy:

innermost




We number the DPs as follows:
  1. LT(s(x), s(y)) -> LT(x, y)
and get the following Size-Change Graph(s):
{1} , {1}
1>1
2>2

which lead(s) to this/these maximal multigraph(s):
{1} , {1}
1>1
2>2

DP: empty set
Oriented Rules: none

We used the order Homeomorphic Embedding Order with Non-Strict Precedence.
trivial

with Argument Filtering System:
s(x1) -> s(x1)

We obtain no new DP problems. 


   R
     ↳OC
       →TRS2
         ↳DPs
           →DP Problem 1
             ↳UsableRules
           →DP Problem 2
             ↳Usable Rules (Innermost)


Dependency Pairs:

APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(member, w), z)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(member, w), x)


Rules:


app(app(lt, app(s, x)), app(s, y)) -> app(app(lt, x), y)
app(app(lt, 0), app(s, y)) -> true
app(app(lt, y), 0) -> false
app(app(eq, x), x) -> true
app(app(eq, app(s, x)), 0) -> false
app(app(eq, 0), app(s, x)) -> false
app(app(member, w), null) -> false
app(app(member, w), app(app(app(fork, x), y), z)) -> app(app(app(if, app(app(lt, w), y)), app(app(member, w), x)), app(app(app(if, app(app(eq, w), y)), true), app(app(member, w), z)))


Strategy:

innermost




As we are in the innermost case, we can delete all 8 non-usable-rules.


   R
     ↳OC
       →TRS2
         ↳DPs
           →DP Problem 1
             ↳UsableRules
           →DP Problem 2
             ↳UsableRules
             ...
               →DP Problem 5
                 ↳A-Transformation


Dependency Pairs:

APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(member, w), z)
APP(app(member, w), app(app(app(fork, x), y), z)) -> APP(app(member, w), x)


Rule:

none


Strategy:

innermost




We have an applicative DP problem with proper arity. Thus we can use the A-Transformation to obtain one new DP problem which consists of the A-transformed TRSs.


   R
     ↳OC
       →TRS2
         ↳DPs
           →DP Problem 1
             ↳UsableRules
           →DP Problem 2
             ↳UsableRules
             ...
               →DP Problem 6
                 ↳Size-Change Principle


Dependency Pairs:

MEMBER(w, fork(x, y, z)) -> MEMBER(w, z)
MEMBER(w, fork(x, y, z)) -> MEMBER(w, x)


Rule:

none


Strategy:

innermost




We number the DPs as follows:
  1. MEMBER(w, fork(x, y, z)) -> MEMBER(w, z)
  2. MEMBER(w, fork(x, y, z)) -> MEMBER(w, x)
and get the following Size-Change Graph(s):
{1, 2} , {1, 2}
1=1
2>2

which lead(s) to this/these maximal multigraph(s):
{1, 2} , {1, 2}
1=1
2>2

DP: empty set
Oriented Rules: none

We used the order Homeomorphic Embedding Order with Non-Strict Precedence.
trivial

with Argument Filtering System:
fork(x1, x2, x3) -> fork(x1, x2, x3)

We obtain no new DP problems.

Termination of R successfully shown.
Duration:
0:01 minutes