Programming Forums > Application Development > C++

ian · Mar 22nd, 2005, 2:13 AM

Okay, I have completely no idea what when wrong, and I also have no idea am I coding in the right way. :o So I'd need someone to help me in this:

This program (currently) takes its program arguments and compares the 1st argument if it's a number, or an operator (+, -, *, /, % or ^). If it's a number, currType will have the value of 1; if it's one of the operator, it'll have the value of 2; all other cases currType will have a value of 3. The problem comes when I attempt to compare the argument with a string. It's kind of difficult to explain, but the code should explain what I want to do. (Line 9 is the problem.)

(Toggle Plain Text)

#include <iostream>
using namespace std;

int main(int argc, char *argv[]) {
    int currType = 0; //0 = null; 1 = num; 2 = operator; 3 = error
    if(atol(argv[1]) != 0) {
        currType = 1;
    }
    else if(argv[1] == "+") {
        currType = 2;
    }
    else {
        currType = 3;
    }
    cout << currType << "::" << argv[1]; //Debugging statement
}

Benoit · Mar 22nd, 2005, 6:07 AM

Correct me if I'm wrong, but you can't compare strings using == thats only for single characters, no?

Mjordan2nd · Mar 22nd, 2005, 6:22 AM

Well, on your first if-statement, I think what you mean to do is

if(argc!=0)

.

On your else if statement, you can't compare strings using the equals sign, like Benoit said. You need to use the strcmp() function in <string.h>.

ian · Mar 23rd, 2005, 6:38 AM

Quote:

Originally Posted by Mjordan2nd

Well, on your first if-statement, I think what you mean to do is

if(argc!=0)

.

On your else if statement, you can't compare strings using the equals sign, like Benoit said. You need to use the strcmp() function in <string.h>.

Done! Thanks for your help. By the way, the first if statement was supposed to check if the arugment was a number. The program would run into an error if there were no arguments, but I've added another if statement to test for arguments. All should go well now, thanks again for you help!

Mar 22nd, 2005, 2:13 AM	#1
ian Newbie Join Date: Feb 2005 Location: Singapore Posts: 13 Rep Power: 0	Help: Comparing a pointer and a string. Okay, I have completely no idea what when wrong, and I also have no idea am I coding in the right way. :o So I'd need someone to help me in this: This program (currently) takes its program arguments and compares the 1st argument if it's a number, or an operator (+, -, , /, % or ^). If it's a number, currType will have the value of 1; if it's one of the operator, it'll have the value of 2; all other cases currType will have a value of 3. The problem comes when I attempt to compare the argument with a string. It's kind of difficult to explain, but the code should explain what I want to do. (Line 9 is the problem.) (Toggle Plain Text) #include <iostream> using namespace std; int main(int argc, char argv[]) { int currType = 0; //0 = null; 1 = num; 2 = operator; 3 = error if(atol(argv[1]) != 0) { currType = 1; } else if(argv[1] == "+") { currType = 2; } else { currType = 3; } cout << currType << "::" << argv[1]; //Debugging statement } #include <iostream> using namespace std; int main(int argc, char *argv[]) { int currType = 0; //0 = null; 1 = num; 2 = operator; 3 = error if(atol(argv[1]) != 0) { currType = 1; } else if(argv[1] == "+") { currType = 2; } else { currType = 3; } cout << currType << "::" << argv[1]; //Debugging statement }

Mar 22nd, 2005, 6:07 AM	#2
Benoit Expert Programmer Join Date: Sep 2004 Location: Ontario, Canada Posts: 550 Rep Power: 4	Correct me if I'm wrong, but you can't compare strings using == thats only for single characters, no? __________________ Johnny was a chemist's son but Johnny is no more, for what Johnny thought was H2O was H2SO4

Mar 22nd, 2005, 6:22 AM	#3
Mjordan2nd The Supreme Ruler Join Date: May 2004 Location: Houston Posts: 1,476 Rep Power: 6	Well, on your first if-statement, I think what you mean to do is if(argc!=0) . On your else if statement, you can't compare strings using the equals sign, like Benoit said. You need to use the strcmp() function in <string.h>. __________________ "Every gun that is made, every warship launched, every rocket signifies, in the final sense, a theft from those who hunger and are not fed, from those who are cold and are not clothed. The world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children." - Dwight D. Eisenhower

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Programming Forums > Application Development > C++

Help: Comparing a pointer and a string.