Thread: Test condition problem,Please help!!!

my test condition in the "ADD MENU" function

Code:

if( (pos = search(ID) )  == -1)

isn't working, thus two profile with the same ID can be added(which im trying to prevent)
I dont understand why becouse it works in my "EDIT" function and "DELETE" function


Just to make debugging faster:


the "search" function returns -1 if an ID doen't esist

Code:

#include <stdio.h>


struct employee
{
       int employee_ID;
       char employee_Name[50];
       int employee_Age;
       char employee_DateOfBirth[20];
       char employee_Address[70];
       char employee_TelNo[20];
       float emplayee_Salary;
       
}employee_array[50]; 




void selection_sort();
int search();
void add_employee();
void edit_employee();
void delete_employee();
void print();
void print_profiles();
void print_profile();
void print_out();
void getstring();


int main(void){
    
    int i,option;
    
    for(i=0;i<50;i++)
          employee_array[i].employee_ID = 0;  
          
    printf("\t\t-------------------------------------------------\n");
    printf("\t\tThis program provides the functionality  \n");
    printf("\t\tto interface with an employee information system.\n");
    printf("\t\t-------------------------------------------------\n\n");         
    
    do{
        printf("\n\n\n\n");
        printf("\t\t ----------------------------------------------\n");
        printf("\t\t|                   MAIN MENU                  |\n");
        printf("\t\t ----------------------------------------------\n\n");
        printf("\t\t[ 1 ]   -   To enter an employee's profile \n");
        printf("\t\t[ 2 ]   -   To edit an employee's profile \n");
        printf("\t\t[ 3 ]   -   To delete an employee's profile \n");
        printf("\t\t[ 4 ]   -   To print an employee's profile \n");
        printf("\t\t[ 0 ]   -   To exit \n\n");
        printf("Please choose an option:\t");
        scanf("%d",&option);  
        switch(option)
                   {
                       case 1: add_employee();
                       break;
                       case 2: edit_employee();
                       break;
                       case 3: delete_employee();
                       break;
                       case 4: print();
                       break;
                       case 0: 
                       break;
                       default:
                       printf("\n\nIncorrect Entry!,Please press enter and Try again!\n\n");
                       getch();
                       break;
                   }   
    }
    while(option != 0);
}


void getstring(char str[] ){ // damn fix this function's glitch
     
     int x=0;
     char ch;
     
     ch=getchar();
     while( (ch=getchar()) !='\n' ){
            str[x++]=ch;
     }
     str[x]= '\0'; 
}


void selection_sort(){
     
     struct employee temp;
     int i,j;
     
     for(i=0;i<50;i++){
          for(j=i+1;j<50;j++){
               if(employee_array[j].employee_ID < employee_array[i].employee_ID)
               {
                      temp = employee_array[j];
                      employee_array[j] =  employee_array[i];
                      employee_array[i] = temp;
               }
          }
     }
     return ;
}


int search(int ID){
     int mid;
     int first = 0;
     int last = 50;


     while(first <= last)
     {
         mid = (first + last)/2;
         if(employee_array[mid].employee_ID == ID)
             return (mid);
         if(ID < employee_array[mid].employee_ID)
            last = mid - 1;
         else
            first = mid +1;
     }
     return -1;
}


 void add_employee(){  //fix this/ ........ing glitch
      
      int pos, ID, age;
      float salary;
      int index = 0;
      char name[50];
      char address[50];
      char telno[50];
      char DOB[20];
      
      printf("\n\n\n\n");
      printf("\t\t ----------------------------------------------\n");
      printf("\t\t|                   ADD MENU                   |\n");
      printf("\t\t ----------------------------------------------\n\n"); 
      printf("\t\tEnter[ 0 ]  -  To return to main menu:\t");
      printf("\n\n\nEnter employee's:\n");
      printf("----------------");
      printf("\n\nID-----------------------: ");
      scanf("%d",&ID);
      
      
          while( ID !=0)
          {
                 if( (pos = search(ID) )  == -1)
                 {
                     employee_array[index].employee_ID = ID;
                     printf("\nName---------------------: ");
                     getstring(name);
                     strcpy(employee_array[index].employee_Name, name);
                     printf("\nDate Of Birth------------: ");
                     getstring(DOB);
                     strcpy(employee_array[index].employee_DateOfBirth, DOB);
                     printf("\nAddress------------------: ");
                     getstring(address);
                     strcpy(employee_array[index].employee_Address, address);
                     printf("\ncontact------------------: ");
                     getstring(telno);
                     strcpy(employee_array[index].employee_TelNo, telno);
                     printf("\nAge----------------------: ");
                     scanf("%d",&age);
                     employee_array[index].employee_Age = age;
                     printf("\nSalary-------------------: ");
                     scanf("%f",&salary);
                     employee_array[index].emplayee_Salary = salary;
                     index++;
                 }
                 else
                     printf("\n\nA profile containing this ID already exist\n");
                 printf("\n\n\nEnter employee's:\n");
                 printf("----------------");
                 printf("\n\nID-----------------------: ");
                 scanf("%d",&ID);
          }
          selection_sort();
 }




void print(){
      
      int option;
    
    do{
        printf("\n\n\n\n");
        printf("\t\t ------------------------------------------------\n");
        printf("\t\t|                   PRINT MENU                   | \n");
        printf("\t\t ------------------------------------------------\n\n");
        printf("\t\t[ 1 ]   -   to print all profiles \n");
        printf("\t\t[ 2 ]   -   to print a specific profile \n");
        printf("\t\t[ 0 ]   -   to return to main menu \n\n");
        printf("Please choose an option:\t");
        scanf("%d",&option);  
        switch(option)
                   {
                       case 1: print_profiles();
                       break;
                       case 2: print_profile();
                       break;
                       case 0: 
                       break;
                       default:
                       printf("\n\nIncorrect Entry!,Please press enter and Try again!\n\n");
                       getch();
                       break;
                   }   
    }while(option !=0);
 }
 
 
void print_profiles(){
     
     int pos,count;
     count = pos = 0;
     
     printf("\n\n\n\n");
     printf("\t\t ----------------------------------------------------\n");
     printf("\t\t|                   SUB PRINT MENU                   |\n");
     printf("\t\t ----------------------------------------------------\n\n");
     for(;pos<50;pos++)
     {
         if(employee_array[pos].employee_ID != 0)
             print_out(pos);
         
     }
     for(pos=0;pos<50;pos++)
     {
         if(employee_array[pos].employee_ID == 0)
             count++;
     }
     if(count == 50)
     {
         printf("\n\n\nNo profile currently exist\n\n");
         printf("Plesae press enter to continue\n");  
         getch();
     } 
}




void print_profile(){
     
     int ID,pos;
     
      printf("\n\n\n\n");
      printf("\t\t -----------------------------------------------\n");
      printf("\t\t|                   SUB PRINT MENU                   |\n");
      printf("\t\t -----------------------------------------------\n\n"); 
      printf("\t\tEnter[ 0 ]  -  To return to print menu");
      printf("\n\n\nEnter employee's:\n");
      printf("----------------");
      printf("\n\nID-----------------------: ");
      scanf("%d",&ID);
     while(ID != 0)
     {
         if( (pos= search(ID) ) != -1)
             print_out(pos);
         else
             printf("\n\nemployee's profile could not be found\n\n");
         printf("\n\n\nEnter employee's:\n");
         printf("----------------");
         printf("\n\nID-----------------------: ");
         scanf("%d",&ID);    
     }
}




void print_out(int pos){
     
     printf("\n\n\nName                ---------------    :    %s",employee_array[pos].employee_Name);
     printf("\n\nAge                 ---------------    :    %d",employee_array[pos].employee_Age);
     printf("\n\nDate Of Birth       ---------------    :    %s",employee_array[pos].employee_DateOfBirth);
     printf("\n\nAddress             ---------------    :    %s",employee_array[pos].employee_Address);
     printf("\n\nTelephone Number    ---------------    :    %s",employee_array[pos].employee_TelNo);
     printf("\n\nSalary              ---------------    :    $%.2f\n\n\n",employee_array[pos].emplayee_Salary);
}




 void edit_employee(){
      
      int pos,ID, age;
      float salary;
      char name[50];
      char address[50];
      char telno[50];
      char DOB[20];
      
      printf("\n\n\n\n");
      printf("\t\t -----------------------------------------------\n");
      printf("\t\t|                   EDIT MENU                   |\n");
      printf("\t\t -----------------------------------------------\n\n"); 
      printf("\t\tEnter[ 0 ]  -  To return to main menu\t");
      printf("\n\n\nEnter employee's:\n");
      printf("----------------");
      printf("\n\nID-----------------------: ");
      scanf("%d",&ID);
      while(ID != 0)
      {
               if( (pos = search(ID)) != -1)
               {
                   employee_array[pos].employee_ID = ID;
                   printf("\nName---------------------: ");
                   getstring(name);
                   strcpy(employee_array[pos].employee_Name, name);
                   printf("\nAge----------------------: ");
                   scanf("%d",&age);
                   employee_array[pos].employee_Age = age;
                   printf("\nDate Of Birth------------: ");
                   getstring(DOB);
                   strcpy(employee_array[pos].employee_DateOfBirth, DOB);
                   printf("\nAddress------------------: ");
                   getstring(address);
                   strcpy(employee_array[pos].employee_Address, address);
                   printf("\ncontact------------------: ");
                   getstring(telno);
                   strcpy(employee_array[pos].employee_TelNo, telno);
                   printf("\nSalary-------------------: ");
                   scanf("%f",&salary);
                   employee_array[pos].emplayee_Salary = salary;
               }
               else
                   printf("\n\nNo profiles containing this ID was found");
               printf("\n\n\nEnter employee's:\n");
               printf("----------------");
               printf("\n\nID-----------------------: ");
               scanf("%d",&ID);
      }
      selection_sort();
}
 
 
void delete_employee(){
      
      int pos,ID;
      
      printf("\n\n\n\n");
      printf("\t\t -------------------------------------------------\n");
      printf("\t\t|                   DELETE MENU                   |\n");
      printf("\t\t -------------------------------------------------\n\n"); 
      printf("\t\tEnter[ 0 ]  -  To return to main menu\t");
      printf("\n\n\nEnter employee's:\n");
      printf("----------------");
      printf("\n\nID-----------------------: ");
      scanf("%d",&ID);
      while(ID != 0)
      {
               if( (pos = search(ID)) != -1)
               {
                   employee_array[pos].employee_ID = 0;
                   printf("\n\nEmployee's ID have successfully been deleted\n");
               }
               else
                   printf("\n\nEmployee's profile does not exist\n");
               printf("\n\n\nEnter employee's:\n");
               printf("----------------");
               printf("\n\nID-----------------------: ");
               scanf("%d",&ID);
      }
      selection_sort();
}

Your binary search needs work. It always results in -1, which would explain why it "works" when you want to add employees, because the program will always add, but not when you want to edit them, because the employees are always not found. Your employee array is global... which means if you had a few interesting IDs, they'd be among a bunch of zero IDs that affect the search. For example (23, 24, 0, 0, 0 ... ). A zero will be found before any of the interesting ids, and the search ends up proceeding in a wrong direction. The array is sorted if you restrict the range to the number of elements you are actually using but if the search space is ever not sorted binary search will not work.

Sorry, but I've never seen an if clause being used to test an expression like this.
How does it work?

The search function is called first:

(pos = search(ID))

Then that result becomes part of the larger expression in the if condition, so it's as if you wrote:

pos = search(ID);
if (pos == -1)

Oh, very nice, didn't know it could be used that way.
Thanks!

@whiteflags

please explain further - you lost me because i thought my "selection sort" function allows the binary search to work,and the "search" doesn't always return -1 it returns the position of the ID if it's found. Also the "edit" function works just fine, that's why i'm confused as to why "add" isn't working.

@grumpy

i have tested it properly, the reason as to why one works and the other doesn't? is beyond my knowledge, that's why in here now

He explained why it worked:

Editing an entry does not affect the sorting.

Even if you get lucky and the right thing happens for the wrong reasons, the logic is still wrong. You must sort before you search... in this case it might be better if search() calls selection_sort() instead of other client code.

please explain further - you lost me because i thought my "selection sort" function allows the binary search to work,and the "search" doesn't always return -1 it returns the position of the ID if it's found. Also the "edit" function works just fine, that's why i'm confused as to why "add" isn't working.

I was afraid I would get it mixed up. I thought I had explained myself adequately but apparently not.