Certification Problem

Input (COPS 177)

We consider the TRS containing the following rules:

-(+(x,y)) → +(-(x),-(y)) (1)
+(-(x),-(y)) → -(+(x,y)) (2)

The underlying signature is as follows:

{-/1, +/2}

Property / Task

Prove or disprove confluence.

Answer / Result

Yes.

Proof (by csi @ CoCo 2021)

1 Redundant Rules Transformation

To prove that the TRS is (non-)confluent, we show (non-)confluence of the following modified system:

+(-(x),-(y)) → -(+(x,y)) (2)

All redundant rules that were added or removed can be simulated in 4 steps .

1.1 Critical Pair Closing System

Confluence is proven using the following terminating critical-pair-closing-system R:

There are no rules.

1.1.1 R is empty

There are no rules in the TRS. Hence, it is terminating.