private ProgramSet LearnTree(PremSpec <TInput, SyntaxNode> spec)
{
// Case 1: leaf nodes, using `Leaf`.
if (spec.Forall((i, o) => o is Token))
{
#if DEBUG
Log.Tree("Leaf |- {0}", spec);
#endif
Label label;
if (spec.Identical((i, o) => o.label, out label))
{
#if DEBUG
Log.IncIndent();
Log.Tree("label = {0}", label);
#endif
var tokenSpace = Intersect(spec.Select(p => LearnToken(p.Key, p.Value.code)));
#if DEBUG
Log.DecIndent();
#endif
if (!tokenSpace.IsEmpty)
{
return(ProgramSet.Join(Op(nameof(Semantics.Leaf)),
ProgramSet.List(Symbol("label"), Label(label)), tokenSpace));
}
}
// else: Inconsistent specification.
}
// Case 2: nodes/lists, copy a reference from old tree.
if (spec.Forall((i, o) => o.matches.Any()))
{
#if DEBUG
Log.Tree("Copy |- {0}", spec);
Log.IncIndent();
#endif
var refSpecs = spec.FlatMap((i, o) => o.matches);
var refSpaces = new List <ProgramSet>();
#if DEBUG
var total = refSpecs.Count();
var count = 1;
#endif
foreach (var refSpec in refSpecs)
{
#if DEBUG
Log.Tree("{0}/{1} ref |- {2}", count, total, refSpec);
Log.IncIndent();
#endif
var space = LearnRef(refSpec);
if (!space.IsEmpty)
{
refSpaces.Add(space);
break;
}
#if DEBUG
Log.DecIndent();
count++;
#endif
}
#if DEBUG
Log.DecIndent();
#endif
var refSpace = Union(refSpaces);
if (!refSpace.IsEmpty)
{
return(ProgramSet.Join(Op(nameof(Semantics.Copy)), refSpace));
}
}
// Case 3: constructor nodes, using `Node`.
if (spec.Forall((i, o) => o is Node))
{
var childrenSpace = Optional <ProgramSet> .Nothing;
#if DEBUG
Log.Tree("Node |- {0}", spec);
#endif
Label label;
if (spec.Identical((i, o) => o.label, out label))
{
var labelSpace = ProgramSet.List(Symbol("Label"), Label(label));
var childrenSpec = spec.MapOutputs((i, o) => o.GetChildren());
#if DEBUG
Log.IncIndent();
Log.Tree("label = {0}", label);
#endif
int arity;
// Same number of children, learn one-by-one.
if (childrenSpec.Identical((i, cs) => cs.Count(), out arity))
{
#if DEBUG
Log.Tree("children |- {0}", childrenSpec);
Log.IncIndent();
#endif
childrenSpace = LearnChildren(childrenSpec);
#if DEBUG
Log.DecIndent();
#endif
if (childrenSpace.HasValue && !childrenSpace.Value.IsEmpty)
{
return(ProgramSet.Join(Op(nameof(Semantics.Node)),
ProgramSet.List(Symbol("label"), Label(label)), childrenSpace.Value));
}
}
else // Different number of children, try `Append`.
{
#if DEBUG
Log.Tree("append |- {0}", childrenSpec);
Log.IncIndent();
#endif
for (int k = 1; k <= 2; k++)
{
childrenSpace = LearnAppend(childrenSpec, k);
if (childrenSpace.HasValue)
{
break;
}
}
#if DEBUG
Log.DecIndent();
#endif
}
#if DEBUG
Log.DecIndent();
#endif
if (childrenSpace.HasValue && !childrenSpace.Value.IsEmpty)
{
return(ProgramSet.Join(Op(nameof(Semantics.Node)), labelSpace, childrenSpace.Value));
}
}
}
// else: Inconsistent specification.
return(ProgramSet.Empty(Symbol("tree")));
}
