/**
* Function VisitForStatement : it adds the variable used as a loop counter
* to the illegalAssigments list and checks that the begin and end value
* are of type INT. Otherwise it throws an error.
* Param : for statement to check
*/
public object VisitForStmt(Stmt.For stmt)
{
/* Error when trying to use the var of the main loop in a loop inside it */
if (illegalAssignments.Contains(stmt.Name.Text))
{
throw new TypeError(stmt.Name, "Cannot use '" + stmt.Name.Text + "' as a loop counter since it is already in use as a loop counter.");
}
/* Add the loop counter to the illegalAssigments list */
illegalAssignments.Add(stmt.Name.Text);
VALTYPE begin = GetType(stmt.BeginValue);
VALTYPE end = GetType(stmt.EndValue);
if (SymbleTypeTable.ContainsKey(stmt.Name.Text))
{
VALTYPE loopcounter = SymbleTypeTable[stmt.Name.Text];
/* The loop counter must be an INT */
if (loopcounter.Equals(VALTYPE.INT))
{
/* If the begin and end value are INT we check the types of the inside statements */
if (begin.Equals(VALTYPE.INT) && end.Equals(VALTYPE.INT))
{
CheckTypes(stmt.Stmts);
illegalAssignments.Remove(stmt.Name.Text);
return(null);
}
/* The begin or the end value were not INT type */
else
{
throw new TypeError(stmt.ForToken, "The begin and end expression should be " + VALTYPE.INT.ToString()
+ ", got " + begin.ToString() + " and " + end.ToString() + " instead.");
}
}
/* Error if the loop counter is not an INT */
else
{
throw new TypeError(stmt.ForToken, "The loop counter '" + stmt.Name.Text + "' should be " + VALTYPE.INT.ToString()
+ ", got " + loopcounter.ToString() + " instead.");
}
}
else
{
throw new TypeError(stmt.ForToken, "The loop counter '" + stmt.Name.Text + "' is not previous declared");
}
}
/**
* Function VisitForStmt --> "for" <var_ident> "in" <expr> ".." <expr> "do" <stmts> "end" "for"
* It evaluates the beginning and ending value for the variable and interpret each statement in
* the list, also it updates the value of the variable used to count in the symble table
* Also it checks that the loop has at least one statement
* Param : for statement to evaluate
*/
public Object VisitForStmt(Stmt.For stmt)
{
int variable;
string name = stmt.Name.Text;
int beginvalue = (int)Evaluate(stmt.BeginValue).Val;
int endvalue = (int)Evaluate(stmt.EndValue).Val;
/* At least one statement */
if (stmt.Stmts.Count == 0)
{
throw new RuntimeError(stmt.Name, "For loop must have at least one statement.");
}
/* Executing all the statements */
for (variable = beginvalue; variable <= endvalue; variable++)
{
SymbleTable[name] = new Value(VALTYPE.INT, variable);
foreach (Stmt st in stmt.Stmts)
{
Execute(st);
}
}
return(null);
}
