private term(TermKind kind, atom a)
{
Kind = kind;
_atom = a;
_applyF = new Box <term>(default(term));
_applyX = new Box <term>(default(term));
}
public ClueId CreateClue(atom kind, ClueSource source, ClueConstant constant, params ClueId[] dependsOn)
{
foreach (var other in dependsOn)
{
if (other == null)
{
throw new Exception("null is not a clue that you can depend on");
}
if (!_clueKind.ContainsKey(other))
{
throw new Exception("can't depend on a clue that doesn't exist");
}
}
var id = _clueIdGen.GenerateClueId(kind);
_clueKind[id] = kind;
_clueSource[id] = source;
_clueConstant[id] = constant;
_clueDependsOn[id] = dependsOn.ToArray();
foreach (var other in dependsOn)
{
_cluesDependingOn[other].Add(id);
}
_cluesDependingOn[id] = new HashSet <ClueId>();
_clueBestKnownType[id] = types.MostGeneral;
_clueErrors[id] = new List <InferenceError>();
_cluesToUpdate.Add(id);
return(id);
}
private term(term t1, term t2)
{
Kind = TermKind.Apply;
_atom = default(atom);
_applyF = new Box <term>(t1);
_applyX = new Box <term>(t2);
}
public A Generate <A>(atom prefix, Func <atom, int, int, A> build)
{
int count;
if (!_counter.TryGetValue(prefix, out count))
{
count = 0;
}
return(build(prefix, _counter[prefix] = ++count, ++_absolute));
}
public A Generate <A>(atom name, Func <atom, int, int, A> build)
{
if (_alreadyAssignedCount.ContainsKey(name))
{
return(build(name, _alreadyAssignedCount[name], _alreadyAssignedAbs[name]));
}
return(_generator.Generate(name, (p, n, abs) =>
{
_alreadyAssignedCount[p] = n;
_alreadyAssignedAbs[p] = abs;
return build(p, n, abs);
}));
}
// true: occurs check passed (meaning var doesn't occur)
// doesn't produce output beyond "occurs check failed" to avoid generating loads of garbage
// *except when it follows a variable*
private bool OccursCheck(atom var, term t2)
{
if (Failed)
{
throw new Exception("this Vars failed and is in an invalid state");
}
switch (t2.Kind)
{
case TermKind.Atom:
return(true);
case TermKind.Apply:
OccursCheck(var, t2.ApplyF);
if (Failed)
{
return(false);
}
OccursCheck(var, t2.ApplyX);
if (Failed)
{
return(false);
}
return(true);
case TermKind.Var:
if (var == t2.VarName)
{
FailMessage(() => "occurs check failed");
return(false);
}
term bound;
if (_bindings.TryGetValue(t2.VarName, out bound))
{
OccursCheck(var, bound);
FailMessage(() => $"when resolving {t2.VarName} to {bound}");
return(false);
}
return(true);
}
throw new Exception("unreachable case");
}
public static term Var(atom a) => new term(TermKind.Var, a);
public static term Atom(atom a) => new term(TermKind.Atom, a);
public static type Var(atom a) => new type(new term[0], term.Var(a));
public static type Atom(atom a) => new type(new term[0], term.Atom(a));
public ClueId GenerateClueId(atom name) => Generate(name, (p, n, abs) => new ClueId(p, n, abs));
public ClueId GenerateClueId(atom prefix) => Generate(prefix, (p, n, abs) => new ClueId(p, n, abs));
public bool Equals(atom other)
{
return(string.Equals(Value, other.Value));
}