internal virtual int val()
{
if (lookahead.token == Tokens.Covert("VAR"))
{
Token v = lookahead;
match(Tokens.Covert("VAR"));
Token s = sym.get_symbol(v.value);
if (s.token != Tokens.Covert("ERR"))
{
return(s.value);
}
else
{
error("VAR not found");
}
return(0);
}
else if (lookahead.token == Tokens.Covert("NUM"))
{
return(exp());
}
else
{
error("VAR or NUM expected");
return(-1);
}
}
public virtual void print_token(Token t)
{
if (t.token == Tokens.Covert("ERR"))
{
Console.WriteLine("<ERR>");
}
else if (t.token == Tokens.Covert("PLUS"))
{
Console.WriteLine("<PLUS>");
}
else if (t.token == Tokens.Covert("EQUALS"))
{
Console.WriteLine("<EQUALS>");
}
else if (t.token == Tokens.Covert("NUM"))
{
Console.WriteLine("<NUM," + t.value + ">");
}
else if (t.token == Tokens.Covert("VAR"))
{
Console.WriteLine("<VAR," + t.value + ">");
}
else if (t.token == Tokens.Covert("PRINT"))
{
Console.WriteLine("<PRINT>");
}
}
internal virtual void @out()
{
if (lookahead.token == Tokens.Covert("PRINT"))
{
match(Tokens.Covert("PRINT"));
int x = val();
Console.WriteLine(x);
}
}
public virtual Token get_symbol(int id)
{
if (id < symbols.Count)
{
return(symbols[id]);
}
Token s = new Token();
s.token = Tokens.Covert("ERR");
return(s);
}
internal virtual int exp()
{
if (lookahead.token == Tokens.Covert("NUM"))
{
int x = lookahead.value;
match(Tokens.Covert("NUM"));
int y = rst();
return(x + y);
}
return(0);
}
internal virtual void pr2()
{
if (lookahead.token == Tokens.Covert("EOL"))
{
match(Tokens.Covert("EOL"));
prg();
}
else if (lookahead.token != Tokens.Covert("EOF"))
{
error("EOL Expected");
}
}
internal virtual void atr()
{
if (lookahead.token == Tokens.Covert("VAR"))
{
int v = lookahead.value;
match(Tokens.Covert("VAR"));
match(Tokens.Covert("EQUALS"));
int x = val();
if (!sym.update_symbol(v, x))
{
error("Impossible assign value");
}
else
{
error("VAR Expected");
}
}
}
internal virtual void cmd()
{
if (lookahead.token == Tokens.Covert("NUM"))
{
exp();
}
else if (lookahead.token == Tokens.Covert("VAR"))
{
atr();
}
else if (lookahead.token == Tokens.Covert("PRINT"))
{
@out();
}
else if (lookahead.token != Tokens.Covert("EOF"))
{
error("Unrecongnized Command");
}
}
internal virtual Token next_Token()
{
Token t = new Token();
Symbols symbol = new Symbols();
t.token = -1;
peek = next_char();
do
{
if (peek == ' ' || peek == '\t')
{
continue;
}
else if (peek == '\n')
{
line++;
char_pos = -1;
}
else
{
break;
}
} while (peek == next_char());
if (peek == '$')
{
string @var = "$";
peek = next_char();
while (isLetter(peek))
{
@var += peek;
peek = next_char();
}
input_pos--;
t.token = Tokens.Covert("VAR");
Token s = new Token();
s.token = Tokens.Covert("VAR");
s.value = 0;
s.lexem = @var;
t.value = symbol.add_symbol(s);
return(t);
}
else if (isDigit(peek))
{
int x = 0;
do
{
x = 10 * x + System.identityHashCode(peek);
peek = next_char();
} while (isDigit(peek));
input_pos--;
t.token = Tokens.Covert("NUM");
t.value = x;
return(t);
}
else if (peek == 'p')
{
string print = "print";
for (int i = 0; i < print.Length; i++)
{
if (print[i] == peek)
{
peek = next_char();
}
else
{
t.token = Tokens.Covert("ERR");
return(t);
}
}
t.token = Tokens.Covert("PRINT");
return(t);
}
else if (peek == ';')
{
t.token = Tokens.Covert("EOL");
t.value = 0;
}
else if (peek == '+')
{
t.token = Tokens.Covert("PLUS");
t.value = 0;
}
else if (peek == '=')
{
t.token = Tokens.Covert("EQUALS");
t.value = 0;
}
return(t);
}