Checking equivalence in a non-strict language

Program equivalence checking is the task of confirming that two programs have same behavior on corresponding inputs. We develop a calculus based symbolic execution and coinduction to check in non-strict functional language. Additionally, we show our can be used derive counterexamples for pairs inequivalent programs, including arise from non-termination. describe fully automated approach finding both proofs counterexamples. Our implementation, Nebula, proves equivalences written Haskell. demonstrate Nebula's practical effectiveness at proving producing automatically by applying Nebula existing benchmark properties.