private static bool ExactlyOnce(object[] args, TextBuffer output, BindingEnvironment env, MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.Check("ExactlyOnce", 1, args);
TextBuffer finalOutput = output;
BindingList <LogicVariable> finalBindings = null;
State finalState = State.Empty;
MethodCallFrame finalFrame = predecessor;
bool failure = true;
var chain = Step.ChainFromBody("ExactlyOnce", args);
chain.Try(output, env,
(o, u, d, p) =>
{
failure = false;
finalOutput = o;
finalBindings = u;
finalState = d;
finalFrame = p;
return(true);
},
predecessor);
if (failure)
{
var failedCall = (Call)chain;
throw new CallFailedException(env.Resolve(failedCall.Task), env.ResolveList(failedCall.Arglist));
}
return(k(finalOutput, finalBindings, finalState, finalFrame));
}
private static bool Not(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
{
foreach (var arg in args)
{
if (!Term.IsGround(arg))
{
throw new ArgumentInstantiationException("Not", e, args, "Use NotAny if you intend goals that aren't ground.");
}
}
// Whether the call to args below succeeded
var success = false;
// This always fails, since its continuation fails too
Step.ChainFromBody("Not", args)
.Try(o, e,
(newOut, newE, newK, newP) =>
{
// Remember that we succeeded, then fail
success = true;
return(false);
},
predecessor);
// If the call to args succeeded, fail; otherwise call continuation
return(!success && k(o, e.Unifications, e.State, predecessor));
}
private static bool IgnoreOutput(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
{
return(Step.ChainFromBody("IgnoreOutput", args).Try(
o, e,
(_, u, s, p) => k(o, u, s, p),
predecessor));
}
private static bool NotAny(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
{
// Whether the call to args below succeeded
var success = false;
// This always fails, since its continuation fails too
Step.ChainFromBody("NotAny", args)
.Try(o, e,
(newOut, newE, newK, newP) =>
{
// Remember that we succeeded, then fail
success = true;
return(false);
},
predecessor);
// If the call to args succeeded, fail; otherwise call continuation
return(!success && k(o, e.Unifications, e.State, predecessor));
}
private static bool Implies(object[] args, TextBuffer output, BindingEnvironment env, MethodCallFrame predecessor, Step.Continuation k)
{
if (args.Length < 2)
{
throw new ArgumentCountException(nameof(Implies), 2, args);
}
var producer = args[0];
var producerChain = Step.ChainFromBody(nameof(Implies), producer);
var consumer = args.Skip(1).ToArray();
var consumerChain = Step.ChainFromBody(nameof(Implies), consumer);
var dynamicState = env.State;
var resultOutput = output;
var allTrue = true;
producerChain.Try(resultOutput, env,
(o, u, d, p) =>
{
// We've got a solution to the producer in u.
// So run the consumer once with u but not d or o.
allTrue &= consumerChain.Try(resultOutput,
new BindingEnvironment(env, u, dynamicState),
(o2, u2, d2, newP) =>
{
// Save modifications to dynamic state, output; throw away binding state
dynamicState = d2;
resultOutput = o2;
// Accept this one solution to consumer; don't backtrack it.
return(true);
},
p);
// Backtrack to generate the next solution for producer
return(false);
},
predecessor);
// Use original unifications but accumulated output and state.
return(allTrue && k(resultOutput, env.Unifications, dynamicState, predecessor));
}
/// <summary>
/// Calls all the tasks in the body and allows the user to provide their own continuation.
/// The only (?) use case for this is when you want to forcibly generate multiple solutions
/// </summary>
internal static void GenerateSolutionsFromBody(string callingTaskName, object[] body, TextBuffer o, BindingEnvironment e,
Step.Continuation k,
MethodCallFrame predecessor)
{
Step.ChainFromBody(callingTaskName, body).Try(o, e, k, predecessor);
}
private static bool And(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
=> Step.ChainFromBody("And", args).Try(o, e, k, predecessor);