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));
}
public override bool Try(TextBuffer output, BindingEnvironment e, Continuation k,
MethodCallFrame predecessor)
{
if (!e.TryCopyGround(Value.Eval(e), out var expValue))
{
// You can't set a variable to a non-ground value
throw new ArgumentInstantiationException("set", e,
new[] { (object)GlobalVariable, Value });
}
if (LocalVariable == null)
{
return(Continue(output,
new BindingEnvironment(e,
e.Unifications,
e.State.Bind(GlobalVariable, expValue)),
k, predecessor));
}
if (e.Unify(LocalVariable, expValue, out var result))
{
return(Continue(output,
new BindingEnvironment(e, result, e.State),
k, predecessor));
}
return(false);
}
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 Parse(object[] args, TextBuffer output, BindingEnvironment env,
MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.CheckAtLeast(nameof(Parse), 2, args);
var call = ArgumentTypeException.Cast <object[]>(nameof(Parse), env.Resolve(args[0]), args);
var text = ArgumentTypeException.Cast <string[]>(nameof(Parse), env.Resolve(args[1]), args);
if (!(call[0] is Task task))
{
throw new InvalidOperationException(
"Task argument to Parse must be a compound task, i.e. a user-defined task with methods.");
}
var taskArgs = new object[call.Length - 1];
var i = 0;
for (var callIndex = 1; callIndex < call.Length; callIndex++)
{
taskArgs[i++] = call[callIndex];
}
var parseBuffer = TextBuffer.MakeReadModeTextBuffer(text);
return(task.Call(taskArgs, parseBuffer, env, predecessor,
(buffer, u, s, p) => buffer.ReadCompleted && k(output, u, s, p)));
}
private static bool Call(object[] args, TextBuffer output, BindingEnvironment env,
MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.CheckAtLeast(nameof(Call), 1, args);
var call = ArgumentTypeException.Cast <object[]>(nameof(Call), args[0], args);
if (!(call[0] is Task task))
{
throw new InvalidOperationException(
"Task argument to Call must be a task");
}
var taskArgs = new object[call.Length - 1 + args.Length - 1];
var i = 0;
for (var callIndex = 1; callIndex < call.Length; callIndex++)
{
taskArgs[i++] = call[callIndex];
}
for (var argsIndex = 1; argsIndex < args.Length; argsIndex++)
{
taskArgs[i++] = args[argsIndex];
}
return(task.Call(taskArgs, output, env, predecessor, k));
}
/// <summary>
/// Run any remaining steps in the chain, otherwise run the continuation.
/// </summary>
/// <returns>True if all steps in the chain, and the continuation are all successful. False means we're backtracking</returns>
protected bool Continue(TextBuffer p, BindingEnvironment e, Continuation k, MethodCallFrame predecessor)
{
if (Next != null)
{
return(Next.Try(p, e, k, predecessor));
}
return(k == null || k(p, e.Unifications, e.State, predecessor));
}
/// <summary>
/// Make a new binding environment with the specified components
/// </summary>
public BindingEnvironment(Module module, MethodCallFrame frame,
BindingList <LogicVariable> unifications, State state)
{
Module = module;
Frame = frame;
Unifications = unifications;
State = state;
}
internal MethodCallFrame(Method method, BindingList <LogicVariable> bindings, LogicVariable[] locals, MethodCallFrame caller, MethodCallFrame predecessor)
{
Method = method;
BindingsAtCallTime = bindings;
Locals = locals;
Caller = caller;
Predecessor = predecessor;
StackDepth = predecessor?.StackDepth + 1 ?? 0;
if (StackDepth > MaxStackDepth)
{
throw new StackOverflowException("Maximum interpreter stack depth in Step program");
}
}
private static bool PreviousCall(object[] args, TextBuffer output, BindingEnvironment env,
MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.Check(nameof(PreviousCall), 1, args);
if (args[0] is LogicVariable)
{
// [PreviousCall ?var]
foreach (var priorGoal in predecessor.GoalChain)
{
var e = priorGoal.CallExpression;
if (env.Unify(args[0], e, out BindingList <LogicVariable> unifications) &&
k(output, unifications, env.State, predecessor))
{
return(true);
}
}
return(false);
}
// [PreviousCall [Task ?args]]
var call = ArgumentTypeException.Cast <object[]>(nameof(PreviousCall), args[0], args);
foreach (var priorGoal in predecessor.GoalChain)
{
if (priorGoal.Method.Task != call[0])
{
// Don't bother making the call expression and trying to unify.
continue;
}
var e = priorGoal.CallExpression;
if (call.Length == e.Length &&
env.UnifyArrays(call, e, out BindingList <LogicVariable> unifications) &&
k(output, unifications, env.State, predecessor))
{
return(true);
}
}
return(false);
}
private static bool Once(object[] args, TextBuffer output, BindingEnvironment env, MethodCallFrame predecessor, Step.Continuation k)
{
TextBuffer finalOutput = output;
BindingList <LogicVariable> finalBindings = null;
State finalState = State.Empty;
MethodCallFrame finalFrame = predecessor;
bool success = false;
GenerateSolutionsFromBody("Once", args, output, env,
(o, u, d, p) =>
{
success = true;
finalOutput = o;
finalBindings = u;
finalState = d;
finalFrame = p;
return(true);
},
predecessor);
return(success && k(finalOutput, finalBindings, finalState, finalFrame));
}
/// <summary>
/// Attempt to run this method
/// </summary>
/// <param name="args">Arguments from the call to the method's task</param>
/// <param name="output">Output buffer to write to</param>
/// <param name="env">Variable binding information</param>
/// <param name="k">Continuation to call if method succeeds</param>
/// <param name="pre">Predecessor frame</param>
/// <returns>True if the method and its continuation succeeded</returns>
public bool Try(object[] args, TextBuffer output, BindingEnvironment env, MethodCallFrame pre, Step.Continuation k)
{
// Make stack frame for locals
var locals = new LogicVariable[LocalVariableNames.Length];
for (var i = 0; i < LocalVariableNames.Length; i++)
{
locals[i] = new LogicVariable(LocalVariableNames[i]);
}
var newFrame = new MethodCallFrame(this, env.Unifications, locals, env.Frame, pre);
MethodCallFrame.CurrentFrame = newFrame;
var newEnv = new BindingEnvironment(env, newFrame);
if (newEnv.UnifyArrays(args, ArgumentPattern, out BindingEnvironment finalEnv))
{
env.Module.TraceMethod(Module.MethodTraceEvent.Enter, this, args, output, finalEnv);
newFrame.BindingsAtCallTime = finalEnv.Unifications;
var traceK = env.Module.Trace == null
? k
: (newO, newU, newState, predecessor) =>
{
MethodCallFrame.CurrentFrame = newFrame;
env.Module.TraceMethod(Module.MethodTraceEvent.Succeed, this, args, newO,
new BindingEnvironment(finalEnv, newU, newState));
MethodCallFrame.CurrentFrame = newFrame.Caller;
return(k(newO, newU, newState, predecessor));
};
if (StepChain?.Try(output, finalEnv, traceK, newFrame) ?? traceK(output, finalEnv.Unifications, finalEnv.State, newFrame))
{
return(true);
}
}
MethodCallFrame.CurrentFrame = newFrame;
env.Module.TraceMethod(Module.MethodTraceEvent.MethodFail, this, args, output, finalEnv);
return(false);
}
private static bool UniqueCall(object[] args, TextBuffer output, BindingEnvironment env,
MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.CheckAtLeast(nameof(UniqueCall), 1, args);
var call = ArgumentTypeException.Cast <object[]>(nameof(PreviousCall), args[0], args);
if (!(call[0] is Task task))
{
throw new InvalidOperationException(
"Task argument to UniqueCall must be a task.");
}
var taskArgs = new object[call.Length - 1 + args.Length - 1];
var i = 0;
for (var callIndex = 1; callIndex < call.Length; callIndex++)
{
taskArgs[i++] = call[callIndex];
}
for (var argsIndex = 1; argsIndex < args.Length; argsIndex++)
{
taskArgs[i++] = args[argsIndex];
}
var fullCall = call;
if (args.Length > 1)
{
fullCall = new object[taskArgs.Length + 1];
fullCall[0] = task;
for (var j = 0; j < taskArgs.Length; j++)
{
fullCall[j + 1] = taskArgs[j];
}
}
if (task.Call(taskArgs, output, env, predecessor,
(o, u, s, newPredecessor) =>
{
foreach (var priorGoal in predecessor.GoalChain)
{
if (priorGoal.Method.Task != task)
{
// Don't bother making the call expression and trying to unify.
continue;
}
if (env.Unify(fullCall, priorGoal.CallExpression, u, out BindingList <LogicVariable> _))
{
// We already did a call that matches this call
// So have the continuation return false, forcing the task.Call above to backtrack
// and try to generate a new solution
return(false);
}
}
return(k(o, u, s, newPredecessor));
}))
{
return(true);
}
return(false);
}
public override bool Try(TextBuffer output, BindingEnvironment e, Continuation k, MethodCallFrame predecessor)
{
foreach (var branch in EffectiveBranches)
{
if (branch == null) // Empty branch, e.g. [case ?x] Something : Something [else] [end]
{
if (Continue(output, e, k, predecessor))
{
return(true);
}
}
else if (branch.Try(output, e,
(o, u, d, newP) =>
Continue(o, new BindingEnvironment(e, u, d), k, newP)
, predecessor))
{
return(true);
}
}
return(false);
}
/// <summary>
/// Find all solutions to the specified sequence of calls. Return a list of the text outputs of each solution.
/// </summary>
internal static List <string[]> AllSolutionTextFromBody(string callingTaskName, object[] body, TextBuffer o,
BindingEnvironment e, MethodCallFrame predecessor)
{
var results = new List <string[]>();
var initialLength = o.Length;
GenerateSolutionsFromBody(callingTaskName, body, o, e,
(output, b, d, p) =>
{
var chunk = new string[output.Length - initialLength];
for (var i = initialLength; i < output.Length; i++)
{
chunk[i - initialLength] = o.Buffer[i];
}
results.Add(chunk);
return(false);
},
predecessor);
return(results);
}
private static bool Or(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
=> args.Any(call =>
{
var tuple = ArgumentTypeException.Cast <object[]>("Or", call, args);
return(Eval(tuple, o, e, predecessor, k, "Or"));
});
/// <summary>
/// Calls a task with the specified arguments 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 GenerateSolutions(string taskName, object[] args, TextBuffer o, BindingEnvironment e, Step.Continuation k, MethodCallFrame predecessor)
{
new Call(StateVariableName.Named(taskName), args, null).Try(o, e, k, 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 SaveText(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.Check("SaveText", 2, args);
var textVar = e.Resolve(args[1]);
if (textVar == null)
{
throw new ArgumentInstantiationException("SaveText", e, args);
}
var invocation = args[0] as object[];
if (invocation == null || invocation.Length == 0)
{
throw new ArgumentTypeException("SaveText", typeof(Call), args[0], args);
}
var arglist = new object[invocation.Length - 1];
Array.Copy(invocation, 1, arglist, 0, arglist.Length);
var call = new Call(invocation[0], arglist, null);
var initialLength = o.Length;
string[] chunk = null;
var frame = predecessor;
if (call.Try(o, e,
(output, b, d, p) =>
{
frame = p;
chunk = new string[output.Length - initialLength];
Array.Copy(o.Buffer, initialLength, chunk, 0, output.Length - initialLength);
return(true);
},
predecessor) &&
e.Unify(textVar, chunk, e.Unifications, out var newUnifications))
{
return(k(o, newUnifications, e.State, frame));
}
return(false);
}
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 IEnumerable <string> DoAll(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor)
=> AllSolutionTextFromBody("DoAll", args, o, e, predecessor).SelectMany(strings => strings);
/// <summary>
/// Make a new binding environment based on the specified environment, with the specified change(s)
/// </summary>
internal BindingEnvironment(BindingEnvironment e, MethodCallFrame frame)
: this(e.Module, frame, e.Unifications, e.State)
{
}
private static bool FindUnique(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
{
ArgumentCountException.Check("FindUnique", 3, args);
var solution = args[0];
var call = args[1] as object[];
if (call == null || call.Length == 0)
{
throw new ArgumentException("Invalid goal expression");
}
var task = ArgumentTypeException.Cast <Task>("FindUnique", call[0], args);
var taskArgs = call.Skip(1).ToArray();
var result = args[2];
var resultSet = new HashSet <object>();
task.Call(taskArgs, o, e, predecessor, (newO, u, s, p) =>
{
resultSet.Add(e.Resolve(solution, u));
return(false);
});
return(e.Unify(result, resultSet.ToArray(), out var final) &&
k(o, final, 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>
/// Make a new binding environment based on the specified environment, with the specified change(s)
/// </summary>
internal BindingEnvironment(Module module, MethodCallFrame frame)
: this(module, frame, null, State.Empty)
{
}
/// <summary>
/// Attempt to run this task
/// </summary>
/// <param name="output">Output to which to write text</param>
/// <param name="env">Variable binding information</param>
/// <param name="k">Continuation to call at the end of this step's step-chain</param>
/// <param name="predecessor">Predecessor frame</param>
/// <returns>True if this steps, the rest of its step-chain, and the continuation all succeed.</returns>
public override bool Try(TextBuffer output, BindingEnvironment env, Continuation k, MethodCallFrame predecessor)
{
MethodCallFrame.CurrentFrame = env.Frame;
var target = env.Resolve(Task);
var arglist = env.ResolveList(Arglist);
return(CallTask(output, env, k, target, arglist, target, predecessor));
}
public override bool Try(TextBuffer output, BindingEnvironment e, Continuation k, MethodCallFrame predecessor)
{
var collectionValue = e.Resolve(collectionVariable);
switch (collectionValue)
{
case Cons list:
{
return(list != Cons.Empty &&
e.Unify(element, list.First, out var bindings) &&
Continue(output,
new BindingEnvironment(e,
bindings,
e.State.Bind(collectionVariable, list.Rest)),
k, predecessor));
}
case ImmutableStack <object> stack:
{
return(!stack.IsEmpty &&
e.Unify(element, stack.Peek(), out var bindings) &&
Continue(output,
new BindingEnvironment(e,
bindings,
e.State.Bind(collectionVariable, stack.Pop())),
k, predecessor));
}
case ImmutableQueue <object> queue:
{
return(!queue.IsEmpty &&
e.Unify(element, queue.Peek(), out var bindings) &&
Continue(output,
new BindingEnvironment(e,
bindings,
e.State.Bind(collectionVariable, queue.Dequeue())),
k, predecessor));
}
default:
throw new ArgumentTypeException("removeNext", typeof(Cons), collectionValue,
new[] { "removeNext", collectionValue });
}
}
private static bool Min(object[] args, TextBuffer o, BindingEnvironment e, MethodCallFrame predecessor, Step.Continuation k)
{
return(MaxMinDriver("Min", args, -1, o, e, k, predecessor));
}
private bool CallTask(TextBuffer output, BindingEnvironment env, Continuation k, object target, object[] arglist,
object originalTarget, MethodCallFrame predecessor)
{
switch (target)
{
case Task p:
return(p.Call(arglist, output, env, predecessor,
(newOutput, u, s, newPredecessor) => Continue(newOutput, new BindingEnvironment(env, u, s), k, newPredecessor)));
case string[] text:
return(Continue(output.Append(text), env, k, predecessor));
case IDictionary d:
ArgumentCountException.Check(d, 2, arglist);
var arg0 = arglist[0];
var v0 = arg0 as LogicVariable;
var arg1 = arglist[1];
if (v0 == null)
{
return(d.Contains(arg0) &&
env.Unify(arg1, d[arg0], out var u) &&
Continue(output,
new BindingEnvironment(env, u, env.State), k, predecessor));
}
else
{
// Arg 0 is out
foreach (DictionaryEntry e in d)
{
if (env.Unify(arg0, e.Key, out var unif1) &&
env.Unify(arg1, e.Value, unif1, out var unif2) &&
Continue(output, new BindingEnvironment(env, unif2, env.State), k, predecessor))
{
return(true);
}
}
}
return(false);
case IList l:
// If it's a list in the operator position, pretend it's a call to member
if (arglist.Length != 1)
{
throw new ArgumentCountException("<list member>", 1, arglist);
}
if (arglist[0] is LogicVariable l0)
{
foreach (var e in l)
{
if (Continue(output,
new BindingEnvironment(env, BindingList <LogicVariable> .Bind(env.Unifications, l0, e),
env.State),
k,
predecessor))
{
return(true);
}
}
}
else
{
if (l.Contains(arglist[0]) && Continue(output, env, k, predecessor))
{
return(true);
}
}
return(false);
case LogicVariable v:
throw new ArgumentException($"Attempt to call an unbound variable {v}");
case null:
throw new ArgumentException($"Null is not a valid task in call {CallSourceText(originalTarget, arglist)}");
case bool b:
if (arglist.Length != 0)
{
throw new ArgumentCountException(b, 0, arglist);
}
return(b && Continue(output, env, k, predecessor));
default:
if (arglist.Length == 0)
{
var hook = env.Module.FindTask(MentionHook, 1, false);
if (hook != null)
{
return(MakeCall(hook, target, Next).Try(output, env, k, predecessor));
}
return(Continue(output.Append(target.ToString()), env, k, predecessor));
}
throw new ArgumentException($"Unknown task {target} in call {CallSourceText(originalTarget, arglist)}");
}
}
/// <summary>
/// Core implementation of both Max and Min
/// </summary>
private static bool MaxMinDriver(string taskName, object[] args,
int multiplier, TextBuffer o, BindingEnvironment e,
Step.Continuation k,
MethodCallFrame predecessor)
{
var scoreVar = args[0] as LogicVariable;
if (scoreVar == null)
{
throw new ArgumentInstantiationException(taskName, e, args);
}
var bestScore = multiplier * float.NegativeInfinity;
var bestFrame = predecessor;
CapturedState bestResult = new CapturedState();
var gotOne = false;
GenerateSolutionsFromBody(taskName, args.Skip(1).ToArray(), o, e,
(output, u, d, p) =>
{
gotOne = true;
var env = new BindingEnvironment(e, u, d);
var maybeScore = env.Resolve(scoreVar);
float score;
switch (maybeScore)
{
case int i:
score = i;
break;
case float f:
score = f;
break;
case double df:
score = (float)df;
break;
case LogicVariable _:
throw new ArgumentInstantiationException(taskName, new BindingEnvironment(e, u, d), args);
default:
throw new ArgumentTypeException(taskName, typeof(float), maybeScore, args);
}
if (multiplier * score > multiplier * bestScore)
{
bestScore = score;
bestResult = new CapturedState(o, output, u, d);
bestFrame = p;
}
// Always ask for another solution
return(false);
},
predecessor);
// When we get here, we've iterated through all solutions and kept the best one.
// So pass it on to our continuation
return(gotOne &&
k(o.Append(bestResult.Output), bestResult.Bindings, bestResult.State, bestFrame));
}