Thread: I forget c for a long time.

I pick up c today for a short exercise.
Tons of error, be ashamed.

Code:

// removechar.cpp : main project file.

#include "stdafx.h"
#include <string>
#include <iostream>
using namespace std;


String removechar(String s, char c) {
   String r = "";
   for (int i = 0; i < strlen(s); i ++) {
      if (s.at(i) != c) r += s.at(i);
      }
   return r;
}


int main() {
	String s;
     removechar re = new removechar();
     s=re.removechar("abcdefg","f");
}

Error 1 error C2146: syntax error : missing ';' before identifier 'removechar'
...
thanks for help

Code:

#include "stdafx.h"
#include <string>
#include <iostream>
using namespace std;

string removechar(char *s, char c) {
   char *r;
   for (int i = 0; i < strlen(s); i ++) {
      if (s.at(i) != c) r += s.at(i);
      }
   return r;
}

int main() {
	char s[];
    s=removechar("abcdefg",'f');
}

I modified it, still get some errors.
please give me an advice.
read up on C/C++ basics is helpful but too slow.

There are so many wrong things with that code, I don't know where to start...
You should really read up on some basics, because you can't continue like this. Everything you're doing is wrong.
I could point out all mistakes, but...
Okay, let me try to point them out.

First:

Code:

   char *r;

Unitialized pointer. Pointer to unowned memory. Pointer to non-existant buffer.

Code:

      if (s.at(i) != c)

s is of type char* - it's NOT a class! You can't call member functions of built-in types. Either use the index operator or declare it as "string s":

Code:

string s;
s.at(i)

or

Code:

s[i]

Code:

 r += s.at(i);

For s.at, refer to above. As for "r +=" - all you're doing is incrementing the pointer address (if the compiler even will allow that, I don't know).
This is a POINTER, so to access the memory, you have to dereference it, like *r. HOWEVER, that's not all. Since this isn't a string class, you need to use string functions such as strcpy or strcat to copy/append strings.

Code:

	char s[];
    s=removechar("abcdefg",'f');

First, why are you declaring s as char[] when you're returning a "string"? Second, there's no such thing as dynamic arrays for built-in types as char. You can't declare a variable of type char[]. It must be a fixed amount, so that's not even possible. If not using a class, you'd return a pointer to the string (char*) where the string is on the heap.

As I pointed out, you're lacking basics. You can't program with this little knowledge you have.

Code:

// removechar.cpp : main project file.

#include "stdafx.h"
#include <string>
#include <iostream>
using namespace std;


char *removechar(char *s, char c) {
   char *r;
   int j;
   for (int i = 0; i < strlen(s); i ++) {
	   if (s[i] != c) {
		  j= i;
			  r[i] = s[j];}
	   else{
		   j=i+1;
		   r[i] = s[j];
	   }
      }
   return r;
}

int main() {
	char *s;
    s=removechar("abcdefg",'f');
	cout<<s;
}

almost there!
Warning 1 warning C4018: '<' : signed/unsigned mismatch
Warning 2 warning C4700: uninitialized local variable 'r'

...You're not listening. r is not pointing to a buffer.

Code:

char* removechar(char* s, char c)
{
	char* r = new char[ strlen(s) + 1 ]; // YOU MUST HAVE A BUFFER OR A POINTER TO A BUFFER IF YOU'RE GOING TO MODIFY THE MEMORY
	int j = 0; // Keep track of the position in the buffer pointed by r
	for (int i = 0; i < strlen(s); i++) // Loop until the end of string s
		if (s[i] != c) r[j++] = s[i]; // If the char at pos i in string s is not equal to c then assign that char to the position j in the buffer r and increment j
	r[j] = '\0'; // Put a NULL char at the end of the string. All string function expect a C-string to end with a NULL char
	return r; // Return out newly created buffer
}

int main()
{
	char* s = removechar("abcdefg", 'f'); // Remove 'f' from the string "abcdefg" ("abcdefg" IS NOT A BUFFER) and assign the returned buffer to s
	cout << s; // Print the contents of s to the console or wherever the default outstream is pointing to.
	delete [] s; // VERY IMPORTANT: DELETE OUT BUFFER NOW THAT WE'RE FINISHED WITH IT.
}

Watch that code carefully and read the comments.

If you insist on using strlen() instead of string.size(), you need to include <cstring>.
So far your 2nd version was the best.
Forget about char* and char[] types; that's C, use std::string instead.

Here are some hints:
- Use the string::find() function to find the char you want to remove.
- Use the string::erase() function to delete the char from the string.
- Here's a good function signature to use: void RemoveChar( std::string& str, char c )