reading string

TurtleFace · 12-07-2007, 03:44 PM

could someone please tell me when the getline inside the else does not work.

Code:

#include <iostream>
#include <string>
#include <cctype>
using namespace std;

void optimal(int len, string input) {}
void least(int len, string input) {}
void first(int len, string input) {}
void clock(int len, string input) {}

int main() {
    string input;
    char token = ' ', in[256];
    int length, other, index = 0, x = 0;
    cout << "Welcome to my Caching Algorithm Simulator.\n" << endl;
    cout << "Enter 0 for default string or 1 to enter custom stream: ";
    length = cin.get();
    cout << length << "\n\n";
    if (length == '0') {
	input = "2 3 2 1 5 2 4 5 3 2 5 2";
	}
    else {
	cout << "Enter your page address stream.\n> ";
	cin.getline ( in, 256 ); 

	}
    cout << "\nPlease choose your algorithm o(pt), l(ru), f(ifo), c(lock): ";
	cout << "\n\n\nKLFD: " << in;
    while (x == 0) {
	cin >> token;
	switch (tolower(token)) {
	    case 'o':	optimal(length, input);
			x++;
			break;

	    case 'l':	least(length, input);
			x++;
			break;

	    case 'f':	first(length, input);
			x++;
			break;

	    case 'c':	clock(length, input);
			x++;
			break;

	    default:	cout << "\n\nSorry you entered incorrect option." << endl;
			cout << "o, l, f, or c: ";
			break;
	    }
	}
    //print board
    return 0;
    }

rsashok · 12-07-2007, 04:05 PM

There are few things to consider:
1. I think you mixed up variable names 'in' and 'input'
2. When using "cin.getline( in, 256 )" how do you know how many char's are really there? Default delimeter '\n' is not written into the the variable. Might be a problem if first input of 'length' differs from number of char's in 'input[]'
3. If default string is used it ends with '\0', custom string ends with nothing.

TurtleFace · 12-07-2007, 04:21 PM

the problem im having is that when the code reaches getline it does nothing and is skipped over. i had the delimeter '\n' in before i just took it out when i was messing aroudn tryign to get it to work

rsashok · 12-07-2007, 05:24 PM

I am not sure, but try not to use name 'input' or 'in' - those might be dangerous words. Call your inptut buffer, let say, buf[256], or anything you prefer which can't be a name of some standard method or function.

ntubski · 12-07-2007, 06:48 PM

I don't think that in or input are names of any standard C(++) function.

The first problem is when you do

Code:

 length = cin.get();

it read 1 character, but only returns after the user presses enter. This means when you call getline it just reads the newline character from before and puts an empty string into in. This is actually similar to the issue in this thread: http://www.linuxquestions.org/questi...orithm-603752/

To take care of this you can use itream's ignore method.

The second problem is that you are reading into the in buffer and displaying it (even when it is uninitialized which could cause crashes!), but you are actually using the string input as data to your functions.

I suggest you get rid of in altogether, since you can read a line directly into a string like this:

Code:

 getline(cin, input);

this also takes care of lines longer than 256 bytes.