public ParserType Visit(ParserApp app)
{
var lambdaType = app.Lambda.Accept(this);
var expr = app.Expression.Accept(this);
if (!(lambdaType is ParserLambdaType))
{
throw new ArgumentException("In an application left expression must be a lambda. Type: " + lambdaType.ToString());
}
ParserLambdaType lambda = lambdaType as ParserLambdaType;
if (!lambda.InputType.Equivalent(expr))
{
throw new ArgumentException(String.Format(
"In an application the type of the right expression must match the type of the bound variable " +
"Expr type: {0} Variable type: {1}",
expr.ToString(), lambda.InputType.ToString()));
}
ParserType logicType = new ParserLogicType();
app.Type = logicType;
return(logicType);
}
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");
}
}