Clingo treats operations that were assumed to be “invalid” not as
processing errors but as operations returning an empty set.
This changes how formulas have to be evaluated. This commit implements
an explicit function for retrieving the return type of an expression,
that is, both the domain of the result as well as whether it’s an empty,
unit, or general set with multiple values.
The “general” domain wasn’t really about general variables, but meant as
a distinction from integer variables. For this reason, this commit
renames the “general” domain to “noninteger.”
This moves the commonly enum classes EvaluationResult, OperationResult,
and Tristate to the Utils header file to avoid code duplication.
Additionally, the SimplificationResult class is replaced by the
semantically similar OperationResult.
Patrick Lühne