C++

Forum

 
Compiler Error with Char

SwanSong (10)
I am working on a project that takes in a Name and a Year group to run functions on, however I keep on getting a compiler crash in one statement of my code. It should take in the username via cin and then run an iterater until the first none-alpha character is found and set it to a Space. This is so it can be concatenated with another char variable later in the script.


Line 9 is what is giving me the error.

1
2
3
4
5
6
7
8
9
10
11
12
 
char cUserName[20]; 
cin >> cUserName; 
int i = 0;
while (i < 20) {
   if (!isalpha(cUserName[i]) {
          i++
   }
   else {
      cUserName[i] = " ";
      break;
   }
}


Its giving me an error of "Could not convert const char* to char". This is on a Win32 system running GCC via MinGW.

Any help or adivce would be really appreciated :)

SwanSong
Scipio (446)
cUserName[i] = ' '

You need to use ' instead of " when using char
SwanSong (10)
yep that solved that!! But now the program spits out garbage! I modified the loop slightly to se what happened at got this:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
 
Please enter the Username you wish to ban: Jamie

value of i is: 0and its char value is:
value of i is: 1and its char value is: a
value of i is: 2and its char value is: m
value of i is: 3and its char value is: i
value of i is: 4and its char value is: e
value of i is: 5and its char value is:
value of i is: 6and its char value is: ┴
value of i is: 7and its char value is: w
value of i is: 8and its char value is:  
value of i is: 9and its char value is:  
value of i is: 10and its char value is:  
value of i is: 11and its char value is:  
value of i is: 12and its char value is: )
value of i is: 13and its char value is: N


Anyone have any idea what could be causing this kinda of output??
Scipio (446)
can you upload the new loop please?
SwanSong (10)
course... here's the full working code as it stands:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
 
#include <windows.h>
#include <stdlib.h>
#include <iostream>
#include <cctype>
using namespace std;

int main()
{
    char cUserName[20];
    char cYearGrp[4];
    cout << "Please enter the Username you wish to ban: ";
    cin >> cUserName;
    cout << "\nPlease enter the users Intake Year: ";
    cin >> cYearGrp;
    
    int i = 0;
    while (i < 20) {
      if (!isalnum(cUserName[i]) || !ispunct(cUserName[i])) {
          cout << "value of i is: " << i;
          cout << "and its char value is: " << cUserName[i] << endl;
          i++;
      }
      else {
        cUserName[i] = ' ';
        break;
      }
    }
    cout << "The string is: " << cUserName << endl;
    strcat(cUserName, cYearGrp);
    
    system("PAUSE");
    //CreateProcess('cmd.exe', szCmdLine);
    return 0;    
}
SwanSong (10)
Its a pattern that seems to repeat, just tried it with nick as the input instead and that gave pretty much exactly the same:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
 
Please enter the Username you wish to ban: nick

Please enter the users Intake Year: 2004
value of i is: 0and its char value is:
value of i is: 1and its char value is: i
value of i is: 2and its char value is: c
value of i is: 3and its char value is: k
value of i is: 4and its char value is:
value of i is: 5and its char value is: (
value of i is: 6and its char value is: ┴
value of i is: 7and its char value is: w
value of i is: 8and its char value is:  
value of i is: 9and its char value is:  
value of i is: 10and its char value is:  
value of i is: 11and its char value is:  
value of i is: 12and its char value is: )
value of i is: 13and its char value is: N


I could understand this if the char cUserName[20]; was uninitated and contained garbage, but as its not being decl'd or new'd I'm not sure why this would output as it does (or why it breaks down before 19 >.> )
Scipio (446)
You dont updat i when char[i] is a space (if i understand your code well, i dont know isalnum() and ispunct())

It goes wrong with the first space... (and the first letter)
Smok006 (34)
So...ur problem is that cYearGrp has the length 4 in stead of 5. Let's say year 2000....in a str it really is: {'2','0','0','0','\0'}.

By the way....I think u'd better init those 2 char arrays: 
1
2
3
4
 

    char cUserName[20]="";
    char cYearGrp[4]="";

Last edited on
SwanSong (10)
Scipio

Right I see... the functions are not properly picking up what I am asking it. My idea is this:


1
2
3
4
 
Normal Code
Input: Jamie
Input: 2004
Strcat: Jamie2004

1
2
3
4
5
 
My Code
Input: Jamie
Input: 2004
Loop
Strcat: Jamie 2004


Because the loop is doing what it is supposed to be it sets my first value cUserName[i] to a space... probably caused by it not properly being initiated.

Smoke006

Yeah that probably didn't help :)

When I initiated the string as you suggested it worked... I was working under the assumption that it would initiate anyway unless I specified something like new or decl (I've come out of PHP) but that obviously isn't the case!

Thanks for the help guys :)

SwanSong
Zaita (2770)
Do you have to use C conventions for your project? Because you have potential buffer-overflow there that would cause your app to crash and allow potential un-authorized code to be executed.
SwanSong (10)
Not especially if I understand what you mean... for instance if a user tries to type in more than can be handled by my cUserName and cYearGrp variables?

How would you suggest preventing this kind of situation??

Zaita (2770)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
 
#include <string>
#include <iostream>

using namespace std;

int main() {
 string name = "";
 string date = "";
 cout << "Please enter name:";
 cin >> name;
 cout << "Please enter date:";
 cin >> date;

 cout << string(name+date) << endl;

 return 0;
}
SwanSong (10)
Ah right, using String methods over Char... I'll have to give it a test :)
Topic archived. No new replies allowed.