Termination of the given GTRS could be disproven:

(0) Obligation:

Generalized rewrite system (where rules with free variables on rhs are allowed):
The TRS R consists of the following rules:

and(tt) → X
__(__(X, Y), Z) → __(X, __(Y, Z))
__(X, nil) → X
__(nil, X) → X
isNePal(__(I, __(P, I))) → tt

(1) CritRuleProof (EQUIVALENT transformation)

The rule and(tt) → X contains free variables in its right-hand side. Hence the TRS is not-terminating.

(2) FALSE