C++ Program to implement Symbol Table - GeeksforGeeks

11 Sep, 2018
Prerequisite: Symbol Table
A Symbol table is a data structure used by the compiler, where each identifier in program’s source code is stored along with information associated with it relating to its declaration. It stores identifier as well as it’s associated attributes like scope, type, line-number of occurrence, etc.
Symbol table can be implemented using various data structures like:
LinkedList
Hash Table
Tree
A common data structure used to implement a symbol table is HashTable.
Operations of Symbol table – The basic operations defined on a symbol table include:
Consider the following C++ function:
// Define a global functionint add(int a, int b){int sum = 0;sum = a + b;return sum;}
Symbol Table for above code:
Below is the C++ implementation of Symbol Table using the concept of Hashing with separate chaining:
// C++ program to implement Symbol Table#include <iostream>using namespace std;  const int MAX = 100;  class Node {      string identifier, scope, type;    int lineNo;    Node* next;  public:    Node()    {        next = NULL;    }      Node(string key, string value, string type, int lineNo)    {        this->identifier = key;        this->scope = value;        this->type = type;        this->lineNo = lineNo;        next = NULL;    }      void print()    {        cout << "Identifier's Name:" << identifier             << "\nType:" << type             << "\nScope: " << scope             << "\nLine Number: " << lineNo << endl;    }    friend class SymbolTable;};  class SymbolTable {    Node* head[MAX];  public:    SymbolTable()    {        for (int i = 0; i < MAX; i++)            head[i] = NULL;    }      int hashf(string id); // hash function    bool insert(string id, string scope,                string Type, int lineno);      string find(string id);      bool deleteRecord(string id);      bool modify(string id, string scope,                string Type, int lineno);};  // Function to modify an identifierbool SymbolTable::modify(string id, string s,                         string t, int l){    int index = hashf(id);    Node* start = head[index];      if (start == NULL)        return "-1";      while (start != NULL) {        if (start->identifier == id) {            start->scope = s;            start->type = t;            start->lineNo = l;            return true;        }        start = start->next;    }      return false; // id not found}  // Function to delete an identifierbool SymbolTable::deleteRecord(string id){    int index = hashf(id);    Node* tmp = head[index];    Node* par = head[index];      // no identifier is present at that index    if (tmp == NULL) {        return false;    }    // only one identifier is present    if (tmp->identifier == id && tmp->next == NULL) {        tmp->next = NULL;        delete tmp;        return true;    }      while (tmp->identifier != id && tmp->next != NULL) {        par = tmp;        tmp = tmp->next;    }    if (tmp->identifier == id && tmp->next != NULL) {        par->next = tmp->next;        tmp->next = NULL;        delete tmp;        return true;    }      // delete at the end    else {        par->next = NULL;        tmp->next = NULL;        delete tmp;        return true;    }    return false;}  // Function to find an identifierstring SymbolTable::find(string id){    int index = hashf(id);    Node* start = head[index];      if (start == NULL)        return "-1";      while (start != NULL) {          if (start->identifier == id) {            start->print();            return start->scope;        }          start = start->next;    }      return "-1"; // not found}  // Function to insert an identifierbool SymbolTable::insert(string id, string scope,                         string Type, int lineno){    int index = hashf(id);    Node* p = new Node(id, scope, Type, lineno);      if (head[index] == NULL) {        head[index] = p;        cout << "\n"             << id << " inserted";          return true;    }      else {        Node* start = head[index];        while (start->next != NULL)            start = start->next;          start->next = p;        cout << "\n"             << id << " inserted";          return true;    }      return false;}  int SymbolTable::hashf(string id){    int asciiSum = 0;      for (int i = 0; i < id.length(); i++) {        asciiSum = asciiSum + id[i];    }      return (asciiSum % 100);}  // Driver codeint main(){    SymbolTable st;    string check;    cout << "**** SYMBOL_TABLE ****\n";      // insert 'if'    if (st.insert("if", "local", "keyword", 4))        cout << " -successfully";    else        cout << "\nFailed to insert.\n";      // insert 'number'    if (st.insert("number", "global", "variable", 2))        cout << " -successfully\n\n";    else        cout << "\nFailed to insert\n";      // find 'if'    check = st.find("if");    if (check != "-1")        cout << "Identifier Is present\n";    else        cout << "\nIdentifier Not Present\n";      // delete 'if'    if (st.deleteRecord("if"))        cout << "if Identifier is deleted\n";    else        cout << "\nFailed to delete\n";      // modify 'number'    if (st.modify("number", "global", "variable", 3))        cout << "\nNumber Identifier updated\n";      // find and print 'number'    check = st.find("number");    if (check != "-1")        cout << "Identifier Is present\n";    else        cout << "\nIdentifier Not Present";      return 0;}
**** SYMBOL_TABLE ****

if inserted -successfully
number inserted -successfully

Identifier's Name:if
Type:keyword
Scope: local
Line Number: 4
Identifier Is present

if Identifier is deleted

number Identifier updated

Identifier's Name:number
Type:variable
Scope: global
Line Number: 3
Identifier Is present

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