/// <summary>
/// <Factor>::= <number> | ( <expr> ) | {+|-} <factor>
/// <variable> | TRUE | FALSE
/// </summary>
public Exp Factor(COMPILATION_CONTEXT ctx)
{
TOKEN l_token;
Exp RetValue = null;
if (Current_Token == TOKEN.TOK_NUMERIC)
{
RetValue = new NumericConstant(GetNumber());
Current_Token = GetToken();
}
else if (Current_Token == TOKEN.TOK_STRING)
{
RetValue = new StringLiteral(last_str);
Current_Token = GetToken();
}
else if (Current_Token == TOKEN.TOK_BOOL_FALSE ||
Current_Token == TOKEN.TOK_BOOL_TRUE)
{
RetValue = new BooleanConstant(
Current_Token == TOKEN.TOK_BOOL_TRUE ? true : false);
Current_Token = GetToken();
}
else if (Current_Token == TOKEN.TOK_OPAREN)
{
Current_Token = GetToken();
RetValue = Expr(ctx); // Recurse
if (Current_Token != TOKEN.TOK_CPAREN)
{
Console.WriteLine("Missing Closing Parenthesis\n");
throw new Exception();
}
Current_Token = GetToken();
}
else if (Current_Token == TOKEN.TOK_PLUS || Current_Token == TOKEN.TOK_SUB)
{
l_token = Current_Token;
Current_Token = GetToken();
RetValue = Factor(ctx);
if (l_token == TOKEN.TOK_PLUS)
{
RetValue = new UnaryPlus(RetValue);
}
else
{
RetValue = new UnaryMinus(RetValue);
}
}
else if (Current_Token == TOKEN.TOK_UNQUOTED_STRING)
{
///
/// Variables
///
String str = base.last_str;
SYMBOL_INFO inf = ctx.TABLE.Get(str);
if (inf == null)
{
throw new Exception("Undefined symbol");
}
GetNext();
RetValue = new Variable(inf);
}
else
{
Console.WriteLine("Illegal Token");
throw new Exception();
}
return(RetValue);
}