public IEnumerable <IAssignmentLiteral> Flatten()
{
// Start by flattening all of the parameters
var flattenedParameters = _parameters.Select(param => param.Flatten().ToArray()).ToArray();
// Get the list of variables that the parameters are assigned to
var parameterTargets = flattenedParameters.Select(list => list.First().Variable);
// Merge any parameter assignments that assign to the same value
var eliminator = new AssignmentEliminator(flattenedParameters.SelectMany(item => item));
eliminator.Eliminate();
parameterTargets = parameterTargets.Select(eliminator.MapVariable);
// Generate the assignment for this term
var target = new Variable();
yield return(new TermAssignment(target, new BoundFunctor(_unbound, parameterTargets)));
// Generate the list of parameter assignments
foreach (var param in eliminator.Assignments)
{
yield return(param);
}
}
/// <summary>
/// Substitutes any variable assignments with their bindings
/// </summary>
public static IEnumerable <IAssignmentLiteral> BindVariables(this IEnumerable <IAssignmentLiteral> withVariables, IBindings bindings)
{
var result = new List <IAssignmentLiteral>();
var extras = new List <IAssignmentLiteral>();
// Run through the assignments
foreach (var assignment in withVariables)
{
if (assignment.Value.UnificationKey == null)
{
// Value is a variable (unifies with everything)
var boundTo = bindings.GetValueForVariable(assignment.Value);
if (boundTo != null)
{
// Flatten the bound value
var flattened = boundTo.Flatten().ToArray();
// Assign the target value of the bound value to the original value location
// Ie, here we have Xn = V and the first value of flattened describes the value of V
// in the form Xm = a(...)
// Substitute Xn = a(...) in the assignment list
// Value of V after resolution can be updated by reading Xn after resolution
var first = (IAssignmentLiteral)flattened[0].RebuildWithParameters(new[] { assignment.Variable, flattened[0].Value });
result.Add(first);
// Add in any extra variables generated by flattening
extras.AddRange(flattened.Skip(1));
}
else
{
// Variable is unbound
result.Add(assignment);
}
}
else
{
result.Add(assignment);
}
}
// Remove any extra items to generate the final result
var eliminator = new AssignmentEliminator(result.Concat(extras));
eliminator.Eliminate();
return(eliminator.Assignments);
}
