Specifically treat convertsTo of LogicalType to ClassifierType, support
convertsTo classifier type w/o specified classifier.
Fix typeOf LogicalItemValueExpression by to rely on logical's type.
Accept LogicalItem in LogicalItemValueExpression's logical slot to enable
replacement of it with an expression at generation time.
LogicalVariableDataForm generates to either a list node or a term.
This choice can be made based on the structure alone.
Logical variable "array" corresponds to list node, everything else to a term.
Usually one uses Splice with LogicalItemExpression wrapping a logical variable.
Using LogicalDataForm wrapping same variable makes Splice unnecessary.
In order to keep code readable these are wrapped again in a cons list.
In general, one should avoid using bare LogicalDataForm, as these are
indistiguishable from normal LogicalVariable.
ExpressionLogicalVariable is replaced with ExpressionItem wrapping
the same expression.
Fixes ensure correct application of transformations.
Late expression can't be used as "placeholder" logical item.
This expression is to be used in those rare cases
when a logical var is to be passed to an external method.
Not available within EvaluationSetting (new marker interface).
Normally logical variable (as an instance of LogicalItem)
is only to be used within a logical context.
Logical item value expr only to contain a logical variable.
LogicalItemValueExpression is to play the same role as valueOf(logical)
within an instance of EvaluationSubject.
LogicalItemExpression is to represent the logical variable itself.
A term may indicate that it "extends" another open term.
An extended term has essentially the same form as the one
being extended, so that they can be unified.
Stronger rules for logical variables scope: constraint rule can't reference logical variable defined in another constraint rule. Logical variable definitions are localized to ConstraintRule template.
Simplify/cleanup the logic of searching for available logical variables.
Fedor Isakov