IEnumerable <CutState> CallPrimitive(Symbol functor, PrologPrimitives.PrimitiveImplementation handler, object[] args, PrologContext context)
{
if (Trace)
{
context.TraceOutput("Goal: {0}", new Structure(functor, args));
}
foreach (var state in handler(args, context))
{
if (Trace)
{
context.TraceOutput((state == CutState.Continue) ? "Succeed: {0}" : "Cut: {0}", new Structure(functor, args));
}
yield return(state);
if (Trace)
{
context.TraceOutput("Retry: {0}", new Structure(functor, args));
}
}
if (Trace)
{
context.TraceOutput("Fail: {0}", new Structure(functor, args));
}
context.PopGoalStack();
}
private ushort StartCallInstruction(PrologContext context, int framePointer, ref ushort pc, out ushort succeedPC,
out IEnumerator <CutState> iterator)
{
int iteratorRegister = code[pc++];
ushort failPC = GetUShort(ref pc);
succeedPC = GetUShort(ref pc);
iterator = null;
// Make the iterator. How we do this depends on the opcode, so re-fetch it.
switch ((Opcode)code[pc - CallTargetOffset])
{
case Opcode.CallWokenGoals:
{
if (context.GoalsHaveWoken)
{
iterator = context.ProveAllWokenGoals().GetEnumerator();
}
}
break;
case Opcode.Call:
{
// It's a user-defined predicate call
PredicateInfo calledPredicate = GetPredicate(ref pc);
PushCallArgs(context, framePointer, predicate.Arity, ref pc);
iterator = calledPredicate.StackCall(context).GetEnumerator();
}
break;
case Opcode.CallPrimitive:
{
// It's a primitive call
PrologPrimitives.PrimitiveImplementation implementation = GetPrimitive(ref pc);
int arity = code[pc++];
PushCallArgs(context, framePointer, arity, ref pc);
iterator =
PrologPrimitives.StackCall(implementation, arity, context).GetEnumerator();
}
break;
default:
Debug.Assert(false, "Bad call opcode");
break;
}
context.SetStack(framePointer, iteratorRegister, iterator);
return(failPC);
}
/// <summary>
/// Prints the byte code for the rule to System.Console.
/// </summary>
public void Disassemble()
{
ushort pc = 0;
while (pc < code.Length)
{
var opcode = (Opcode)code[pc++];
Console.Write("L{0}: {1} ", pc - 1, opcode.ToString());
switch (opcode)
{
case Opcode.MatchStructure:
{
Symbol functor = GetSymbol(ref pc);
int arity = code[pc++];
int endofMatch = GetUShort(ref pc);
Console.Write("{0}/{1}, L{2}, ", functor.Name, arity, endofMatch);
DisassembleOperand(ref pc);
}
break;
case Opcode.MatchVar:
case Opcode.MatchVarFirst:
{
if (opcode == Opcode.MatchVarFirst)
{
Console.Write("{0}, ", GetSymbol(ref pc));
}
byte register = code[pc++];
Console.Write("{0}, ", FormatRegister(register));
DisassembleOperand(ref pc);
}
break;
case Opcode.MatchLiteral:
{
Console.Write(GetLiteral(ref pc));
Console.Write(", ");
DisassembleOperand(ref pc);
}
break;
case Opcode.BuildStructure:
{
Console.Write(GetSymbol(ref pc));
Console.Write("/{0}, ", code[pc++]);
DisassembleOperand(ref pc);
}
break;
case Opcode.BuildVar:
{
Console.Write(GetSymbol(ref pc));
Console.Write(", ");
DisassembleOperand(ref pc);
}
break;
case Opcode.BuildReg:
{
byte reg = code[pc++];
Console.Write("{0}, ", FormatRegister(reg));
DisassembleOperand(ref pc);
}
break;
case Opcode.BuildLiteral:
{
Console.Write(GetLiteral(ref pc));
DisassembleOperand(ref pc);
}
break;
case Opcode.Call:
case Opcode.CallPrimitive:
case Opcode.CallWokenGoals:
{
Console.Write("{0}", FormatRegister(code[pc++]));
Console.Write(", {0}", FormatLabel(GetUShort(ref pc)));
Console.Write(", {0}", FormatLabel(GetUShort(ref pc)));
if (opcode != Opcode.CallWokenGoals)
{
int arity;
if (opcode == Opcode.Call)
{
PredicateInfo p = GetPredicate(ref pc);
Console.Write(", {0}/{1}", p.Name, p.Arity);
arity = p.Arity;
}
else
{
PrologPrimitives.PrimitiveImplementation impl = GetPrimitive(ref pc);
arity = code[pc++];
Console.Write(", {0}/{1}", PrologPrimitives.PrimitiveName(impl), arity);
}
while (arity-- > 0)
{
Console.Write(", ");
int arg = code[pc++];
if (arg < 0x80)
{
Console.Write("{0}", FormatRegister(arg)); // It's a register
}
else
{
// It's a literal
arg = ((arg & 0x7f) << 8) + code[pc++];
Console.Write(GlobalLiteralTable[arg]);
}
}
}
}
break;
default:
throw new Exception("Unknown opcode " + opcode);
}
Console.WriteLine();
}
}
