Programming Forums > Application Development > C++

d_heyzie · Apr 16th, 2006, 1:40 AM

Hey again, im learning about data structures in c++ and all was fine until i attempted to make a program using arrays in data structures. Anyways it's a program that asks for input for names and ages and displays it when 5 names and ages have been input. i think my problem is in the for loop that asks for input. (MAX = 5):

(Toggle Plain Text)

 
for(i = 0; i < MAX; i++)
   {
          cout <<" Enter Name: ";
          cin.getline(member[i].name, 99);
          cout << endl;
          cout <<" Enter Age: ";
          cin >> member[i].age;
          cout << endl << endl;
    }

The problem is that when i input the first name and age it prompts again for name and age but it seems to have automattically put in a blank name so it only really asks for age input.

(Toggle Plain Text)

 for(i = 0; i < MAX; i++)
    {
          cout <<" Enter Name: ";
          cin >> member[i].name;
          cout << endl;
          cout <<" Enter Age: ";
          cin >> member[i].age;
          cout << endl << endl;
    }

In this snippet i have replaced "cin.getline(member[i].name, 99);" with
"cin >> member[i].name;" and it works fine except it only displays one field, becuase of cin i guess. I have tried to change member into a 2d array with no success (maybe i did it wrong) please help!! ty.

grumpy · Apr 16th, 2006, 1:53 AM

The reason for what you see in the first snipper is that the cin>>member[i].age reads an integer, and stops when it encounters input that is not an integer .... i.e. the '\n' you have hit. On the next time through the loop, the cin.getline() call sees that newline, reads it, and assumes it has received the whole line.

In the second snippet, the cin >> .... operations read until they get the next whitespace. It will work fine unless the user enters a name that contains whitespace. You might also find it entertaining to see what happens with the second snippet if you enter a name with a space in it (eg "Joe Bloggs").

The better approach would be to use the getline() method and parse the string you receive for data (eg the name and age).

d_heyzie · Apr 16th, 2006, 9:31 AM

Sry not sure what you mean by parse (only learned some definitions for it 2 minutes ago)

(Toggle Plain Text)

  for(i = 0; i < MAX; i++)
    {
          cout <<" Enter Name: ";
          cin.getline(member[i].name, 99);
          cout << endl;
          cout <<" Enter Age: ";
          cin.getline(member[i].age, 99);
          atoi(member[i].age);
          cout << endl << endl;
    }

But while i was offline i changed a few things by asking for input in the form of a character array and then changing it into an integer, and it works fine
ty for your help.

DaWei · Apr 16th, 2006, 9:47 AM

Some input functions are also required to perform conversions. If a conversion is not possible, they are going to run off into the weeds and puke in their cuff. When you use such a function you should ask it immediately if it has barfed. Anything less is just foolish and schlocky, unless you hold absolute power over your users.

grumpy · Apr 16th, 2006, 10:01 AM

Computer science definition of "parse" : To analyze or separate input into more easily processed components.

Apr 16th, 2006, 1:40 AM	#1
d_heyzie Newbie Join Date: Jan 2006 Posts: 22 Rep Power: 0	Arrays in data structures Hey again, im learning about data structures in c++ and all was fine until i attempted to make a program using arrays in data structures. Anyways it's a program that asks for input for names and ages and displays it when 5 names and ages have been input. i think my problem is in the for loop that asks for input. (MAX = 5): (Toggle Plain Text) for(i = 0; i < MAX; i++) { cout <<" Enter Name: "; cin.getline(member[i].name, 99); cout << endl; cout <<" Enter Age: "; cin >> member[i].age; cout << endl << endl; } for(i = 0; i < MAX; i++) { cout <<" Enter Name: "; cin.getline(member[i].name, 99); cout << endl; cout <<" Enter Age: "; cin >> member[i].age; cout << endl << endl; } The problem is that when i input the first name and age it prompts again for name and age but it seems to have automattically put in a blank name so it only really asks for age input. (Toggle Plain Text) for(i = 0; i < MAX; i++) { cout <<" Enter Name: "; cin >> member[i].name; cout << endl; cout <<" Enter Age: "; cin >> member[i].age; cout << endl << endl; } for(i = 0; i < MAX; i++) { cout <<" Enter Name: "; cin >> member[i].name; cout << endl; cout <<" Enter Age: "; cin >> member[i].age; cout << endl << endl; } In this snippet i have replaced "cin.getline(member[i].name, 99);" with "cin >> member[i].name;" and it works fine except it only displays one field, becuase of cin i guess. I have tried to change member into a 2d array with no success (maybe i did it wrong) please help!! ty.

Apr 16th, 2006, 9:31 AM	#3
d_heyzie Newbie Join Date: Jan 2006 Posts: 22 Rep Power: 0	Sry not sure what you mean by parse (only learned some definitions for it 2 minutes ago) (Toggle Plain Text) for(i = 0; i < MAX; i++) { cout <<" Enter Name: "; cin.getline(member[i].name, 99); cout << endl; cout <<" Enter Age: "; cin.getline(member[i].age, 99); atoi(member[i].age); cout << endl << endl; } for(i = 0; i < MAX; i++) { cout <<" Enter Name: "; cin.getline(member[i].name, 99); cout << endl; cout <<" Enter Age: "; cin.getline(member[i].age, 99); atoi(member[i].age); cout << endl << endl; } But while i was offline i changed a few things by asking for input in the form of a character array and then changing it into an integer, and it works fine ty for your help.

Apr 16th, 2006, 9:47 AM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Some input functions are also required to perform conversions. If a conversion is not possible, they are going to run off into the weeds and puke in their cuff. When you use such a function you should ask it immediately if it has barfed. Anything less is just foolish and schlocky, unless you hold absolute power over your users. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Apr 16th, 2006, 1:53 AM	#2
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,253 Rep Power: 5	The reason for what you see in the first snipper is that the cin>>member[i].age reads an integer, and stops when it encounters input that is not an integer .... i.e. the '\n' you have hit. On the next time through the loop, the cin.getline() call sees that newline, reads it, and assumes it has received the whole line. In the second snippet, the cin >> .... operations read until they get the next whitespace. It will work fine unless the user enters a name that contains whitespace. You might also find it entertaining to see what happens with the second snippet if you enter a name with a space in it (eg "Joe Bloggs"). The better approach would be to use the getline() method and parse the string you receive for data (eg the name and age).

Apr 16th, 2006, 10:01 AM	#5
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,253 Rep Power: 5	Computer science definition of "parse" : To analyze or separate input into more easily processed components.

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Programming Forums > Application Development > C++

Arrays in data structures