/**
* Function VisitVarStmt --> "var" <var_ident> ":" <type> [ ":=" <expr> ]
* It adds the new variable to the SymbleTable
* If it already exists throws an error
* If it is not initialized we put a default value : 0 for ints, "" for strings
* and false for bools
* Param : var statement to evaluate
*/
public Object VisitVarStmt(Stmt.Var stmt)
{
String name = stmt.Name.Text;
VALTYPE type = ExpectedType(stmt);
/* Case the variable is already in the symble table */
if (SymbleTable.ContainsKey(name))
{
throw new RuntimeError(stmt.Name, "This variable already exists.");
}
/* Case the variable is not initialized : assign default values */
else if (stmt.Initializer is null)
{
switch (type)
{
case VALTYPE.INT: SymbleTable.Add(name, new Value(type, 0)); break;
case VALTYPE.STRING: SymbleTable.Add(name, new Value(type, "")); break;
case VALTYPE.BOOL: SymbleTable.Add(name, new Value(type, false)); break;
}
}
/* Case the variable is initialized : evaluate the ini expression */
else
{
SymbleTable.Add(name, Evaluate(stmt.Initializer));
}
return(null);
}
/**
* Function VisitVarStmt : it adds a new variable to the table and checks :
* The variable was not previous declared
* The variable and the initialized value have the same type
* Param : var statement to check
*/
public object VisitVarStmt(Stmt.Var stmt)
{
/* Error if the identifier has been initialized before */
if (SymbleTypeTable.ContainsKey(stmt.Name.Text))
{
throw new TypeError(stmt.Name, "Cannot initialize " + stmt.Name.Text + " more than once.");
}
else
{
/* Check the VALTYPE of the variable and add it to the symble table */
VALTYPE type;
switch (stmt.Type)
{
case TokenKind.Int:
type = VALTYPE.INT;
break;
case TokenKind.String:
type = VALTYPE.STRING;
break;
case TokenKind.Bool:
type = VALTYPE.BOOL;
break;
default:
throw new TypeError(stmt.Name, "Expected a type.");
}
SymbleTypeTable.Add(stmt.Name.Text, type);
/* If the variable is gonna be initialized we check the types */
if (stmt.Initializer != null)
{
VALTYPE right = GetType(stmt.Initializer);
if (SymbleTypeTable[stmt.Name.Text].Equals(right))
{
return(null);
}
/* The type of the identifier and the initialized value are not the same */
else
{
throw new TypeError(stmt.Name, stmt.Name.Text + " is of type " + SymbleTypeTable[stmt.Name.Text] + ", but got " + right.ToString() + " instead.");
}
}
/* The variable is initialized to null so we don't check types */
else
{
return(null);
}
}
}
/**
* Function ExpectedType : it checks the token type of the variable (int,
* string or bool) and it returns its corresponding VALTYPE.
* Param : var statement to check
* Return : the corresponding VALTYPE to each TokenKind or an error
*/
private VALTYPE ExpectedType(Stmt.Var stmt)
{
switch (stmt.Type)
{
case TokenKind.Int: return(VALTYPE.INT);
case TokenKind.String: return(VALTYPE.STRING);
case TokenKind.Bool: return(VALTYPE.BOOL);
default:
throw new RuntimeError(stmt.Name, "Cannot declarate " + stmt.Type.ToString() + " as a variable.");
}
}