Equivalent of sscanf

I'm transitioning from C to C++ and am apparently having issues with certain things. In my C code, I have something that looks like this:

Code:

---

char grid[2][2];
for(int y=0; y<2; y++)
{
    while(scanf("%c %c", &grid[y][0], &grid[y][1]) != 2)
    {
        printf("Please format your input as 2 characters separated by a space\nPress a key to try again\n");
        getch();
    }
}

---

How would I do the same in C++? I tried using cin << grid[y][0] << grid[y][1], but if I type "lolol" or something it doesn't read the data the way I want it to.

Your pointing your thingamajigs in the wrong whatchacallit (sorry to go all technical on you) :

Code:

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    cin >> grid[y][0] >> grid[y][1];

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<< is the "insertion" operator, which inserts data into an output stream.
>> is the "extraction" operator, which extracts data from an input stream.

>> it doesn't read the data the way I want it to.

I would hope not, since the data is clearly wrong.

By default the I/O objects will become zombies if something goes wrong. They can throw exceptions but you have to program which exceptions to throw. In the meantime, you have code like this which will reset the state of I/O objects and generally handle bad input. C++ does give you plenty of methods to work with so you can figure out what happened in the aftermath of an operation and deal with it. iostream - C++ Reference

Code:

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#include <iostream>
#include <cstddef> // for BUFSIZ
while (!(cin >> grid[y][0] >> grid[y][1])) {
    cin.clear();
    cin.ignore(BUFSIZ, '\n');
}

---

Sorry about the wrong thingamajigs and the lack of proper description. That was just example code to quickly show what I'm looking for.

What I'm actually doing is a loop on both x and y and I don't know how to read it without scanf. Here's what I've been trying:

Code:

---

for(int y=0; y<gridsize; y++)
{
    cout << "Map the grid line " << y << endl;
    for(int x=0; x<gridsize; x++) //a perfect square grid
    {
        while(grid[y][x] != 'O' && grid[y][x] != '.')
        {
            cin.get(grid[y][x]);
            if(grid[y][x] != 'O' && grid[y][x] != '.') { cout << "Please enter a O or a ." << endl; }
            cin.ignore(256, ' ');
        }
    }
}

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But while I'm inputting data in the program, it gets all buggy with the newlines and the spaces. I want my program window to look like this:

Code:

---

Map the grid line 0
O b
Please enter a O or a .
O .
Map the grid line 1
...

---

Right now I can bug it out by doing something like this

Code:

---

Map the grid line 1
butt
Please enter a O or a .
Please enter a O or a .
Please enter a O or a .
Please enter a O or a .
O.O
... //The program is ok with this even though it has too many characters

---

With scanf, I can make sure I'm only reading one character and that there is a space inbetween, and if I typed something like "butt O" it would read b and O. I'm looking to do that with C++.

Your description of scanf is incorrect. It won't make sure there's a space between the characters or just read the first letters of the first two words. You must have dreamt that. I often do.

Try this:

Code:

---

#include <stdio.h>
int main(void) {
    char a, b;
    scanf("%c %c", &a, &b);
    printf("[%c] [%c]\n", a, b);
    return 0;
}

---

Input: hello there
Ouput: [h] [e]

Oops! T.T. I think this would work the way I want but I haven't tried it:

Code:

---

char v[2];
scanf("%[^' '] %c", &v[0], &v[1]);

---

Anyway that just further verifies I need to learn to do this, lol

Interesting trick, but unfortunately it's a buffer overflow.

Code:

---

#include <stdio.h>
int main(void) {
    char a, b, c='x', d='x';
    scanf("%[^ ] %c", &a, &b);
    printf("[%c] [%c] [%c] [%c]\n", a, b, c, d);
    return 0;
}

---

Input: hello there
Output: [h] [t] [e] [l]

Note that c and d were overwritten.

I guess the best way to do that in C would be to read the entire line, separate spaces with strtok, and then read only the first letter of each token.

Back to my original question though - how do I read letters, in a for loop, separated by a space in C++? cin.get(grid[y][x]); gets me the letter and then I can verify it, but how do I make sure everything is separated by a space, and how do I ignore full words? cin.ignore(256, ' '); didn't seem to do the trick.

Just read the tokens into std::string variables and verify that they are single characters after the fact.

Code:

---

std::string letter1;
std::string letter2;
std::cin >> letter1 >> letter2;
if (letter1.size() == 1 && letter2.size() == 1)
{
    // you have two letters
    char l1 = letter1[0];
    char l2 = letter2[0];
    // do something with l1, l2
}
else
{
    // there was an input error
}

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Quote:

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Originally Posted by Alexander Edgar

how do I read letters, in a for loop, separated by a space in C++? cin.get(grid[y][x]); gets me the letter and then I can verify it, but how do I make sure everything is separated by a space, and how do I ignore full words? cin.ignore(256, ' '); didn't seem to do the trick.

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Use brewbuck's suggestion in post #9, except that you use it with getline:
std::string letter;

Code:

---

while (std::getline(std::cin, letter, ' '))
{
    if (letter.size() == 1)
    {
        // ...
    }
    else if (letter.empty())
    {
        // separated by multiple spaces - invalid input?
    }
    else
    {
        // ignore full word
    }
}

---

You could also do

Code:

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char letter[2], temp;
if (std::cin >> letter[0] && std::cin >> temp && temp == ' ' && std::cin >> letter[1])
        // Success!
else
        // The user entered some input in the wrong format and/or type. Clear input buffer and try again.

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