public ParserType Visit(ParserBinder binder)
{
// idea: copy our current context, add the new bound variable, visit, remove bound variable
// then merge back into our current context
var newCtx = CloneContext();
newCtx[binder.VariableName] = binder.VariableType;
var visitor = new TypeVisitor(newCtx);
ParserType subExpr = binder.Expr.Accept(visitor);
newCtx.Remove(binder.VariableName);
JoinContext(newCtx);
if (subExpr.Typ != ParserTypeEnum.Logic || !(subExpr is ParserLogicType))
{
throw new ArgumentException("Bound subexpression must be a logical expression. Type: " + subExpr.ToString());
}
var logicalExpr = subExpr as ParserLogicType;
switch (binder.OpType)
{
case ParserBinderType.Exists:
if ((binder.VariableType.Flags & ParserTypeFlags.Overt) == 0)
{
throw new ArgumentException("Exists can only bind overt variables");
}
ParserType logicType = new ParserLogicType();
binder.Type = logicType;
return(logicType);
case ParserBinderType.Lambda:
ParserType newType = new ParserLambdaType(binder.VariableType);
binder.Type = newType;
return(newType);
case ParserBinderType.The:
if (binder.VariableType is ParserNumType)
{
ParserType numType = new ParserNumType();
binder.Type = numType;
return(numType);
}
else
{
throw new ArgumentException("'The' binder can only bind Nat types");
}
default:
throw new ArgumentException("Unknown Binder");
}
}
public Expression Visit(ParserBinder binder)
{
Expression subExpr = binder.Expr.Accept(this);
switch (binder.OpType)
{
case ParserBinderType.Exists:
return(new NumExists(binder.VariableName, subExpr as LogicExpression));
case ParserBinderType.Lambda:
return(new LambdaExpression(binder.VariableName, subExpr as LogicExpression));
case ParserBinderType.The:
return(new NumThe(binder.VariableName, subExpr as LogicExpression));
default:
break;
}
throw new ArgumentException("Unknown binder");
}
