public override bool Unify(BaseTerm t, VarStack varStack)
{
if ((t = t.ChainEnd()) is Variable) // t not unified
{
((Variable)t).Bind(this);
varStack.Push(t);
return(true);
}
if (t is ListPatternTerm && arity == t.Arity) // two ListPatternTerms match if their rangeTerms match
{
for (int i = 0; i < arity; i++)
{
if (!args[i].Unify(t.Args[i], varStack))
{
return(false);
}
}
return(true);
}
if (t is ListTerm)
{
pattern = args; // pattern is searched ...
target = ((ListTerm)t).ToList(); // ... in target
int ip = 0;
int it = 0;
return(UnifyTailEx(ip, it, varStack));
}
return(false);
}
public Variable DeclareGlobalVariable(string name, DObject val)
{
if (variables.ContainsKey(name))
{
throw new InterpreterException(interpreter.CurrentToken, "Global variable already exists: " + name);
}
var stack = new VarStack();
var v = new Variable(val, -1);
stack.Push(v);
variables.Add(name, stack);
return(v);
}
public ReadOnlyVariable DeclareReadOnly(string name, DObject val)
{
var v = new ReadOnlyVariable(val, interpreter.depth);
if (!variables.ContainsKey(name))
{
var stack = new VarStack();
stack.Push(v);
variables.Add(name, stack);
}
variables[name].Push(v);
return(v);
}
public Variable DeclareLocal(string name, DObject val)
{
val = val == null ? DUndefined.instance : val;
var v = new Variable(val, interpreter.depth);
if (!variables.ContainsKey(name))
{
var stack = new VarStack();
stack.Push(v);
variables.Add(name, stack);
}
variables[name].Push(v);
return(v);
}
// UNIFICATION
// The stack is used to store the variables and choice points that are bound
// by the unification. This is required for backtracking. Unify does not do
// any unbinding in case of failure. This will be done during backtracking.
// refUnifyCount: can be used for calculating the 'cost' of a predicate Call
public virtual bool Unify(BaseTerm t, VarStack varStack)
{
NextUnifyCount();
if (t.IsUnified)
{
return(this.Unify(t.ChainEnd(), varStack));
}
if (t is Variable) // t not unified
{
((Variable)t).Bind(this);
varStack.Push(t);
return(true);
}
if (t is ListPatternTerm)
{
return(t.Unify(this, varStack));
}
if (termType != t.termType)
{
return(false); // gives a slight improvement
}
if (functor.Equals(t.functor) && arity == t.arity)
{
for (int i = 0; i < arity; i++)
{
if (!args[i].Unify(t.args[i], varStack))
{
return(false);
}
}
return(true);
}
return(false);
}
