On Coevaluation Behavior and Equivalence

Coevaluation, the coinductive interpretation of standard big-step evaluation rules, is a concise form semantics, with same number rules as in evaluation, which intends to simultaneously describe finite and infinite computations. However, it known that only able express an computations subset, and, date, remains unknown exactly what this subset is. More precisely, coevaluation behavior has several unusual features: there are terms for but do not coevaluate, deterministic sense coevaluate any value v, one value. In work, we be expressed by coevaluation. importantly, introduce extension well-behaved divergence. Consequently, no features presented; particular, captures all (not them). addition, consequence thiswell-behavior, present expected equivalence between (extended) union