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Old Apr 23rd, 2006, 6:42 AM   #1
programmingnoob
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output - 842150451?
i have a hash table that i am using to store tokens (entries being the token name and token code being the attribute) ... if it sees an error token or identifier, then it inserts it into the symbol table
so i am reading from a text file whose first two lines have
[HTML] begin if y=2 then z := 1
else if y=1 then z := 0 else even(y-2) end;[/HTML]
^^^bolded stuff is the problem area
ideally, it should have given me Int and id respectively
but they both give me - 842150451 ....
after tracing it down in my code, what i think the problem is my program ends up finding 1 and z in my hash table which makes sense because it inserted these values when it found them earlier in the text ... what does not make sense is why 842150451 as attribute?? when clearly the attributes of 1 and z had been entered as int and id respectively?

(Toggle Plain Text) 
#include <string>
#include <math.h>

using namespace std;

const int TableSize = 137;


	enum Token {program, var, procedure, // both token and
               begin, end, integer,    // token type
               read, writeln, then,
               If,                 // if is the token
               Else,               // else is the token
               scln,               // ; is the token
               cln,                // : is the token
               cma,                // , is the token
               asgn,               // := is the token
               plus,               // + is the token
               minus,              // - is the token
               mult,               // * is the token
               Div,                // div is the token
               eql,                // = is the token
               neq,                // <> is the token
               lss,                // < is the token
               gtr,                // > is the token
               lp,                 // ( is the token
               rp,                 // ) is the token
               id, Int, String, error, eof};

template <class Attributes>
class item {
	
public:
	    item (string s) {
			name = s;
		}
		string getName (void) {return name;}
		
		struct AT{Token type; int value;} theStruct; 
private:
	string name; 
	};
//template <class Attributes>
			

template <class Attributes>
struct HashNode
	{
		item<Attributes> * info;
		HashNode<Attributes> *Next;
	};


template <class Attributes>
class SymTab 
{
public:
	SymTab<Attributes>();  //initializes to the empty table
	item<Attributes> * find(string s);//returns item pointer or null
	item<Attributes> * insert(string s); //inserts if necessary and returns item pointer
	void init_table(string token, Token code);

private:
	int Hash(string s)
	{
		int i = s.length();
		//if (i<0) i = 0;
		unsigned long string_value = 0;
		for (int pos = 0; pos < i; pos++)
			string_value = string_value + int(s[pos]) * pow(10,pos);
		return string_value%TableSize;
	}
	HashNode<Attributes> * hashtable[TableSize];
};
template <class Attributes>
void SymTab<Attributes>::init_table(string token, Token code)
		{
			item <string> *b;
			b = insert(token);
			b->theStruct.type = code;
			//cout <<b->theStruct.type <<flush;
		}

template <class Attributes>
item<Attributes> * SymTab<Attributes>::find(string s)
{
	int pos = Hash(s);
	//cout << pos <<flush;
	if (hashtable[pos] == NULL) return NULL; //Symbol not found
	HashNode<Attributes> *Current = hashtable[pos];
	if (Current != NULL)
	{while(Current != NULL)
	{
		if (Current->info->getName().compare(s) == 0) 
			return Current->info;
		Current = Current->Next;
	}}
	return NULL;
}

template <class Attributes>
SymTab<Attributes>::SymTab()
{
	for (int i = 0; i<TableSize; i++)
	{
		hashtable[i] = new HashNode<Attributes>;
		hashtable[i] = NULL;
	}
	init_table("program", program);
	init_table("var", var);
	init_table("procedure", procedure);
	init_table("begin", begin);
	init_table("end", end);
	init_table("integer", integer);
	init_table("read", read);
	init_table("writeln", writeln);
	init_table("then", then);
	init_table("if", If);
	init_table("else", Else);
	init_table(";", scln);
	init_table(":", cln);
	init_table(",", cma);
	init_table(":=", asgn);
	init_table(",", cma);
	init_table("+", plus);
	init_table("-", minus);
	init_table("*", mult);
	init_table("/", Div);
	init_table("=", eql);
	init_table("<>", neq);
	init_table("<", lss);
	init_table(">", gtr);
	init_table("(", lp);
	init_table(")", rp);
	//init_table("eof", eof); 

}

template <class Attributes>
item <Attributes> * SymTab <Attributes>::insert(string s) 
{
	int pos = Hash(s);
	if (pos < 1) cout << "skdjk" <<flush;
	
	if (hashtable[pos] == NULL) // Row is empty
	{
		hashtable[pos] = new HashNode<Attributes>;
		hashtable[pos]->info = new item<Attributes>(s);
		hashtable[pos]->Next = NULL;
		
		return hashtable[pos]->info;
	}
	else
	{
		HashNode<Attributes> *Current = hashtable[pos];
		HashNode<Attributes> *nNode;
		if (Current != NULL)
		{while(Current != NULL && Current->Next != NULL) Current = Current->Next;} 
		nNode = new HashNode<Attributes>;
		nNode->info = new item<Attributes>(s);
		nNode->Next = NULL;
		Current->Next = nNode;
		return Current->info;
		 
	}
}

template <class Attributes>
 class Scanner {
              public:
                   Scanner(string s) // s is the name of the input file
				   {
					   fin.open (s.c_str()); 
					   	if (fin.fail()) 
					{
							cout<<"Couldn't open file"<<endl; 
							exit(1);
					}
					}
				   //bool eof(item<string> *l)
				   //{return fin.eof;}
				   item<Attributes>* cget();
				   void sync ()
				   {fin.sync();}
              private:
					item<string>* x;
					item<string>* y;
					SymTab <string> ST1;
                   ifstream fin; // opened by the constructor scanner
				int remWS() // result is first non-white space char
					{int c;
					 do{ c = fin.get();} while(isspace(c)); return c;
					}
				void appnd(char c, string & s) // appends c to the end of s
					{string s1;
					s1 = c;
					s.append(s1);}
					};
template <class Attributes>
 item<Attributes>* Scanner<Attributes>::cget() // returns next token
    { //fin.sync();
	int c;  
	
	string s;
    c = fin.get();
	cout <<"C:"<< c<< endl;
	if (c== -1)
	{cout <<"rightbefore" <<endl;
		x = ST1.insert("end of file");
	x->theStruct.type = eof; 
	return x;}

	else if(c==10)
	{
	c = remWS();
	s = c;
	cout << "new line"<<endl;
	} 

	else if (c==32)
	{
	c = remWS();
	s = c;
	} 
	

	if(c==60)
	{c = fin.get () ;
	if (c==62)
	{x = ST1.find ("<>"); return x;}
	else {x = ST1.find ("<"); fin.putback(c); cout <<"NF"<<endl; return x;}
		 
	}
	
	else if (c==58)
	{c = fin.get () ;
	if (c==61)
	{x = ST1.find (":="); return x;} 
	else {x = ST1.find (":"); fin.putback(c); return x;}
	}		

	else if (c==34)
	{int count = 0;
		while (c != 34 && c != 10)
	{c = fin.get (); appnd (c, s); count++;}
	if (c == 34) { x = ST1.insert(s); x->theStruct.type = String; return x;}
	else {while (count > 0) 
	{fin.putback(c); count--;} 
	string interesting = "interesting" ;
	x = ST1.insert(interesting);
	x -> theStruct.type = error; 
	return x; }}

	else if (c==47)
	{
		c = fin.get();
		
	if (c!=47)
	{  	x = ST1.find ("/"); fin.putback(c);
		return x; 
	}
	else 
	{   while (c != 10 && c != -1) {c = fin.get(); } fin.putback(c);} 
	}


	s = c;
	cout<< "need to sddddd" << s << "DDD"
	x = ST1.find(s);
	
	if (x != NULL){cout<< "need to sddddd" << s << "DDD" ; return x;}
	else { string listen; 
	y = NULL;
	c = fin.get();
	listen = c; 
	y = ST1.find (listen);
	if ((y == NULL) && (c != -1) && (c != 32) && (c != 10))
	{while ((y == NULL) && (c != -1) && (c != 32) && (c != 10))
	{
	appnd (c, s);
	c = fin.get(); 
	listen = c;
	x = ST1.find (s);
	y = ST1.find (listen);} fin.putback(c);}
	else fin.putback (c);
	cout << "need to sddddd" << s << "DDD"<< endl;
	
	if (x != NULL) 
	{return x; }
	else { int size = s.length();
	cout << "size"<< size << endl;	
	int sum = 0;
		char g = s[sum]; 
	 if (isdigit(g))
	 {
		 while (sum < size  && isdigit(g))
	 {sum++; g = s[sum];}
	 if (sum==size)
	 { cout <<"int" << endl;
		 x = ST1.insert (s);
	 x->theStruct.type = Int; 
	 x->theStruct.value = atoi(s.c_str());
	 return x;}
	 else { x = ST1.insert(s);
			x->theStruct.type = error;
			return x;}}
	 else 
	 {int sum = 0;
	 //cout << "id:" <<endl;
	 char h = s[sum];
	 while ((isdigit(h)|isalpha(h)) && sum < size)
	 {sum++; h = s[sum];}
	 if (sum== size)
	{
	 x = ST1.insert(s);
	 x->theStruct.type  = id; 
	 return x;}
	 else {
	 x = ST1.insert(s);
	 x->theStruct.type = error;
	 return x;
	 } }}}}
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Old Apr 23rd, 2006, 3:03 PM   #2
Cache
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I don't have a clue what your code is supposed to be doing, but following is almost certainly an error:

(Toggle Plain Text) 
while ((isdigit(h)|isalpha(h)) && sum < size)

I think you mean:
(Toggle Plain Text) 
while ( (isdigit(h) || isalpha(h)) && (sum < size) )
I just scrolled down your code and spotted that. There may be other errors, too.
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Old Apr 23rd, 2006, 3:55 PM   #3
programmingnoob
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Quote:
Originally Posted by Cache
I don't have a clue what your code is supposed to be doing, but following is almost certainly an error:

(Toggle Plain Text) 
while ((isdigit(h)|isalpha(h)) && sum < size)

I think you mean:
(Toggle Plain Text) 
while ( (isdigit(h) || isalpha(h)) && (sum < size) )
I just scrolled down your code and spotted that. There may be other errors, too.
it's a scanner ... it reads from an input file and throws tokens
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Old Apr 23rd, 2006, 9:23 PM   #4
The Dark
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In the insert function:
(Toggle Plain Text) 
template <class Attributes>
item <Attributes> * SymTab <Attributes>::insert(string s) 
{
  int pos = Hash(s);
  if (pos < 1) cout << "skdjk" <<flush;

  if (hashtable[pos] == NULL) // Row is empty
  {
    hashtable[pos] = new HashNode<Attributes>;
    hashtable[pos]->info = new item<Attributes>(s);
    hashtable[pos]->Next = NULL;

    return hashtable[pos]->info;
  }
  else
  {
    HashNode<Attributes> *Current = hashtable[pos];
    HashNode<Attributes> *nNode;
    if (Current != NULL)
    {while(Current != NULL && Current->Next != NULL) Current = Current->Next;} 
    nNode = new HashNode<Attributes>;
    nNode->info = new item<Attributes>(s);
    nNode->Next = NULL;
    Current->Next = nNode;
    return Current->info;

  }
}

Look at the red line at the end of the function. You are returning the info of the previous entry in the has table, not the newly created one. Change the line to
(Toggle Plain Text) 
    return nNode->info;

Also, you should fix your indenting, how can you work out what is going on when all the ifs and whiles are all jumbled up like that?
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