How to check the value of a char?

[XianForce]

well I was just playing around with what I've learned in C++ so far, and I wanted to make a very very basic text calculator. So I want to have a char and then I want to check its value: Add, Subtract, Multiply, etc.

So how can I check the value of a char...I thought it would be like this:

Code: Select all

char a;
std::cin >> a;
std::cout << std::endl;
if(a==Add)
Add();
if(a==Subtract)
Subtract();

And I think you get the idea. I keep getting an error that Add is an unknown variable. I changed a to a short for now and made 1=add, 2=subtract,etc.

So is there something I missed in my code? ^That's the Gist of it^ Or is there another way to do this?

[jesterguy]

I think this is what you need but not positive
http://www.cplusplus.com/reference/clib ... trcmp.html

[XianForce]

I think this is what you need but not positive
http://www.cplusplus.com/reference/clib ... trcmp.html

That looks like its C.

[jesterguy]

well it worked for me in my text rpg I made awhile ago and it was in c++.

[mokkan]

Why not just use std::string if you're using C++? Here's some code:

Code: Select all

#include <iostream>
#include <string>

using namespace std;

int main() {
    string input;

    cout << "What operation would you like to perform? ";
    cin >> input;

    if(input == "add") {
        cout << "You chose the 'add' operation." << endl;
    } else if (input == "subtract") {
        cout << "You chose the 'subtract' operation." << endl;
    } else if (input == "divide") {
        cout << "You chose the 'divide' operation." << endl;
    } else if (input == "multiply") {
        cout << "You chose the 'multiply' operation." << endl;
    } else {
        cout << "Invalid operation." << endl;
    }

    return 0;
}

[XianForce]

Why not just use std::string if you're using C++? Here's some code:

Code: Select all

#include <iostream>
#include <string>

using namespace std;

int main() {
    string input;

    cout << "What operation would you like to perform? ";
    cin >> input;

    if(input == "add") {
        cout << "You chose the 'add' operation." << endl;
    } else if (input == "subtract") {
        cout << "You chose the 'subtract' operation." << endl;
    } else if (input == "divide") {
        cout << "You chose the 'divide' operation." << endl;
    } else if (input == "multiply") {
        cout << "You chose the 'multiply' operation." << endl;
    } else {
        cout << "Invalid operation." << endl;
    }

    return 0;
}

lol, duh should've used a string, thanks lol

[Trask]

well I was just playing around with what I've learned in C++ so far, and I wanted to make a very very basic text calculator. So I want to have a char and then I want to check its value: Add, Subtract, Multiply, etc.

So how can I check the value of a char...I thought it would be like this:

Code: Select all

char a;
std::cin >> a;
std::cout << std::endl;
if(a==Add)
Add();
if(a==Subtract)
Subtract();

And I think you get the idea. I keep getting an error that Add is an unknown variable. I changed a to a short for now and made 1=add, 2=subtract,etc.

So is there something I missed in my code? ^That's the Gist of it^ Or is there another way to do this?

Keep in mind that char's only hold one character at a time unless you do a char array, plus to check the value of a char it would have to be something like (a = 'A'), note the single quotes.

[avansc]

please use a switch! if else if else if else is such an ugly way to code.

i would have had something like

#define ADD atoi('+') // dont know if that would work, but i just meant the ascii value of a plus sign.
and do the rest so on.
dont use strings for something a char will do just fine. single key strokes should always just be a char. and addition, subtraction, multiplication and division all have their own special buttons on the keyboard. use them, they feel left out.

[MarauderIIC]

In line with avansc, why are you not doing

Code: Select all

cin >> mychar;
switch (mychar) {
    case '+':
        Add(rest of input)
        break;
    case '-':
        Subtract(rest of input);
        break;
};

?

And avansc, you can directly cast from int to char, so #define ADD = '+' //// or in C++, const char ADD = '+' //// or const int ADD = '+' //// would work just fine

[Trask]

If he's going through a C++book, I do believe that everyone that I've read goes to if statements before the almighty switch statement... so maybe that's why he's using IF statements?

[XianForce]

In line with avansc, why are you not doing

Code: Select all

cin >> mychar;
switch (mychar) {
    case '+':
        Add(rest of input)
        break;
    case '-':
        Subtract(rest of input);
        break;
};

?

And avansc, you can directly cast from int to char, so #define ADD = '+' //// or in C++, const char ADD = '+' //// or const int ADD = '+' //// would work just fine

Haven't got there yet xD, I'm a novice, don't know much C++ xD

[MarauderIIC]

Well, I hope you don't plan on enforcing order of operations, because then it gets all recursive and hard =)
Also, read up on switch :). It can only handle types that are equivalent to a number or true/false (in other words, no case "this is my string!" allowed, but case 'a' or case 1 are fine), but it's still really handy.

[XianForce]

Well, I hope you don't plan on enforcing order of operations, because then it gets all recursive and hard =)
Also, read up on switch . It can only handle types that are equivalent to a number or true/false (in other words, no case "this is my string!" allowed, but case 'a' or case 1 are fine), but it's still really handy.

Ya, I'm just going to go in the order the book lays it down for me though, I think they know better than I xD.